Abstract

Accessibility of web content requires semantic information about widgets, structures, and behaviors, in order to allow assistive technologies to convey appropriate information to persons with disabilities. This specification provides an ontology of roles, states, and properties that define accessible user interface elements and can be used to improve the accessibility and interoperability of web content and applications. These semantics are designed to allow an author to properly convey user interface behaviors and structural information to assistive technologies in document-level markup. This document is part of the WAI-ARIA suite described in the WAI-ARIA Overview.

Status of this Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.

This is an Editor's Draft of the Protocols and Formats Working Group. It is not stable and may change at any time. Implementors should not use this for anything other than experimental implementations.

Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

1. Introduction

expanding the accessibility information that may be supplied by the author;

requiring that supporting host languages provide full keyboard support that may be implemented in a device-independent way, for example, by telephones, handheld devices, e-book readers, and televisions;

improving the accessibility of dynamic content generated by scripts; and

WAI-ARIA is a technical specification that provides a framework to improve the accessibility and interoperability of web content and applications. This document is primarily for developers creating custom widgets and other web application components. Please see the WAI-ARIA Overview for links to related documents for other audiences, such as the WAI-ARIA Primer that introduces developers to the accessibility problems that WAI-ARIA is intended to solve, the fundamental concepts, and the technical approach of WAI-ARIA.

This draft currently handles two aspects of roles: user interface functionality and structural relationships. For more information and use cases, see the WAI-ARIA Primer [ARIA-PRIMER] for the use of roles in making interactive content accessible.

The role taxonomy is designed in part to support the common roles found in platform accessibility APIs. Reference to roles found in this taxonomy by dynamic web content may be used to support interoperability with assistive technologies.

The schema to support this standard has been designed to be extensible so that custom roles can be created by extending base roles. This allows user agents to support at least the base role, and user agents that support the custom role can provide enhanced access. Note that much of this could be formalized in XML Schema [XSD]. However, being able to define similarities between roles, such as baseConcepts and more descriptive definitions, would not be available in XSD.

WAI-ARIA Primer [ARIA-PRIMER], a W3C Working Group Note, introduces developers to the accessibility problems that WAI-ARIA is intended to solve, the fundamental concepts, and the technical approach of WAI-ARIA.

1.1. Rich Internet Application Accessibility

The domain of web accessibility defines how to make web content usable by persons with disabilities. Persons with certain types of disabilities use assistive technologies (AT) to interact with content. Assistive technologies can transform the presentation of content into a format more suitable to the user, and can allow the user to interact in different ways. For example, the user may need to, or choose to, interact with a slider widget via arrow keys, instead of dragging and dropping with a mouse. In order to accomplish this effectively, the software needs to understand the semantics of the content. Semantics is the science of meaning; in this case, used to assign roles, states, and properties that apply to user interface and content elements as a human would understand. For instance, if a paragraph is semantically identified as such, assistive technologies can interact with it as a unit separable from the rest of the content, knowing the exact boundaries of that paragraph. An adjustable range slider or collapsible list (a.k.a. a tree widget) are more complex examples, in which various parts of the widget have semantics that need to be properly identified for assistive technologies to support effective interaction.

New technologies often overlook semantics required for accessibility, and new authoring practices often misuse the intended semantics of those technologies. Elements that have one defined meaning in the language are used with a different meaning intended to be understood by the user.

For example, web application developers create collapsible tree widgets in HTML using CSS and JavaScript even though HTML has no semantic tree element. To a non-disabled user, it may look and act like a collapsible tree widget, but without appropriate semantics, the tree widget may not be perceivable to, or operable by, a person with a disability because assistive technologies may not recognize the role.

The incorporation of WAI-ARIA is a way for an author to provide proper semantics for custom widgets to make these widgets accessible, usable, and interoperable with assistive technologies. This specification identifies the types of widgets and structures that are commonly recognized by accessibility products, by providing an ontology of corresponding roles that can be attached to content. This allows elements with a given role to be understood as a particular widget or structural type regardless of any semantic inherited from the implementing host language. Roles are a common property of platform accessibility APIs which assistive technologies use to provide the user with effective presentation and interaction.

Roles are element types and will not change with time or user actions. Role information is used by assistive technologies, through interaction with the user agent, to provide normal processing of the specified element type.

States and properties are used to declare important attributes of an element that affect and describe interaction. They enable the user agent and operating system to properly handle the element even when the attributes are dynamically changed by client-side scripts. For example, alternative input and output technology, such as screen readers and speech dictation software, need to be able to recognize and effectively manipulated and communicate various interaction states (e.g., disabled, checked) to the user.

Figure 1.0 illustrates the relationship between user agents (e.g., browsers), accessibility APIs, and assistive technologies. It describes the "contract" provided by the user agent to assistive technologies, which includes typical accessibility information found in the accessibility API for many of our accessible platforms for GUIs (role, state, selection, event notification, relationship information, and descriptions). The DOM, usually HTML, acts as the data model and view in a typical model-view-controller relationship, and JavaScript acts as the controller by manipulating the style and content of the displayed data. The user agent conveys relevant information to the operating system's accessibility API, which can be used by any assistive technologies, such as screen readers.

In addition to the prose documentation, the role taxonomy is provided in Web Ontology Language (OWL) [OWL], which is expressed in Resource Description Framework (RDF) [RDF]. Tools can use these to validate the implementation of roles in a given content document. For example, instances of some roles are expected to be children of a specific parent role. Also, some roles may support a specific state or property that another role does not support.

Note: The use of RDF/OWL as a formal representation of roles may be used to support future extensibility. Standard RDF/OWL mechanisms can be used to define new roles that inherit from the roles defined in this specification. The mechanism to define and use role extensions in an interoperable manner, however, is not defined by this specification. A future version of WAI-ARIA is expected to define how to extend roles.

Users of alternate input devices need keyboard accessible content. The new semantics, when combined with the recommended keyboard interactions provided in WAI-ARIA Authoring Practices [ARIA-PRACTICES], will allow alternate input solutions to facilitate command and control via an alternate input solution.

WAI-ARIA introduces navigational landmarks through its taxonomy and the XHTML role landmarks, which can help persons with dexterity and vision impairments by providing for improved keyboard navigation. WAI-ARIA may also be used to assist persons with cognitive learning disabilities. The additional semantics allow authors to restructure and substitute alternative content as needed.

Assistive technologies need the ability to support alternative inputs by getting and setting the current value of widget states and properties. Assistive technologies also need to determine what objects are selected and manage widgets that allow multiple selections, such as list boxes and grids.

Speech-based command and control systems can benefit from WAI-ARIA semantics like the role attribute to assist in conveying audio information to the user. For example, by determining that an element has a role of menu and that it contains three elements with the role menuitem each containing text content representing a different flavor, a speech system might state to the user that, "Select one of three choices: chocolate, strawberry, or vanilla."

WAI-ARIA is intended to be used as a supplement for native language semantics, not a replacement. When the host language provides a feature that provides equivalent accessibility to the WAI-ARIA feature, use the host language feature. WAI-ARIA should only be used in cases where the host language lacks the needed role, state, and property indicators. Use a host language feature that is as similar as possible to the WAI-ARIA feature, then refine the meaning by adding WAI-ARIA. For instance, a multi-selectable grid could be implemented as a table, and then WAI-ARIA used to clarify that it is an interactive grid, not just a static data table. This allows for the best possible fallback for user agents that do not support WAI-ARIA and preserves the integrity of the host language semantics.

Each conformance requirement indicates the audience to which it applies.

Although this specification is applicable to the above audiences, it is not specifically targeted to, nor is it intended to be the sole source of information for, any of these audiences. The following documents provide important supporting information:

WAI-ARIA Authoring Practices addresses authoring recommendations, and is also of interest to developers of authoring tools and conformance checkers.

Assistive technologies use the enhanced information available in an accessibility API, or uses the WAI-ARIA markup directly via the DOM, to convey semantic and interaction information to the user.

Aside from using WAI-ARIA markup to improve what is exposed to accessibility APIs, user agents behave as they would natively. Assistive technologies react to the extra information in the accessibility API as they already do for the same information on non-web content. User agents that are not assistive technologies, however, need do nothing beyond providing appropriate updates to the accessibility API.

The WAI-ARIA specification neither requires or forbids user agents from enhancing native presentation and interaction behaviors on the basis of WAI-ARIA markup. Mainstream user agents might expose WAI-ARIA navigational landmarks (for example, as a dialog box or through a keyboard command) with the intention to facilitate navigation for all users. User agents are encouraged to maximize their usefulness to users, including users without disabilities.

WAI-ARIA is intended to provide missing semantics so that the intent of the author may be conveyed to assistive technologies. Generally, authors using WAI-ARIA will provide the appropriate presentation and interaction features. Over time, host languages may add WAI-ARIA equivalents, such as new form controls, that are implemented as standard accessible user interface controls by the user agent. This allows authors to use them instead of custom WAI-ARIA enabled user interface components. In this case the user agent would support the native host language feature. Developers of host languages that implement WAI-ARIA are advised to continue supporting WAI-ARIA semantics when they do not adversely conflict with implicit host language semantics, as WAI-ARIA semantics more clearly reflect the intent of the author if the host language features are inadequate to meet the author's needs.

1.4. Co-Evolution of WAI-ARIA and Host Languages

WAI-ARIA is intended to augment semantics in supporting languages like HTML and SVG, or used as an accessibility enhancement technology in other markup-based languages that do not explicitly include support for ARIA. It clarifies semantics to assistive technologies when authors create new types of objects, via style and script, that are not yet directly supported by the language of the page, because the invention of new types of objects is faster than standardized support for them appears in web languages.

It is not appropriate to create objects with style and script when the host language provides a semantic element for that type of objects. While WAI-ARIA can improve the accessibility of these objects, accessibility is best provided by allowing the user agent to handle the object natively. For example, it's better to use an h1 element in HTML than to use the heading role on a div element.

It is expected that, over time, host languages will evolve to provide semantics for objects that currently can only be declared with WAI-ARIA. This is natural and desirable, as one goal of WAI-ARIA is to help stimulate the emergence of more semantic and accessible markup. When native semantics for a given feature become available, it is appropriate for authors to use the native feature and stop using WAI-ARIA for that feature. Legacy content may continue to use WAI-ARIA, however, so the need for user agents to support WAI-ARIA remains.

While specific features of WAI-ARIA may lose importance over time, the general possibility of WAI-ARIA to add semantics to web pages is expected to be a persistent need. Host languages may not implement all the semantics WAI-ARIA provides, and various host languages may implement different subsets of the features. Furthermore, new types of objects are continually being developed. Therefore, one goal of WAI-ARIA is to provide a way to make such objects accessible, because web authoring practices often advance faster than host language standards. In this way, WAI-ARIA and host languages both evolve together but at different rates.

Some host languages exist to create semantics for features other than the user interface. For example, SVG expresses the semantics behind production of graphical objects, not of user interface components that those objects may represent; XForms provides semantics for form controls and does not provide wider user interface features. Host languages such as these might, by design, not provide native semantics that map to WAI-ARIA features. In these cases, WAI-ARIA could be adopted as a long-term approach to add semantic information to user interface components.

1.5. Authoring Practices

1.5.1. Authoring Tools

Many of the requirements in the definitions of WAI-ARIAroles, states, and properties can be checked automatically during the development process, similar to other quality control processes used for validating code. To assist authors who are creating custom widgets, authoring tools may compare widget roles, states, and properties to those supported in WAI-ARIA as well as those supported in related and cross-referenced roles, states, and properties. Authoring tools may notify authors of errors in widget design patterns, and may also prompt developers for information that cannot be determined from context alone. For example, a scripting library can determine the labels for the tree items in a tree view, but would need to prompt the author to label the entire tree. To help authors visualize a logical accessibility structure, an authoring environment might provide an outline view of a web resource based on the WAI-ARIA markup.

In HTML, tabindex is an important way browsers support keyboard focus navigation for implementations of WAI-ARIA; authoring and debugging tools may check to make sure tabindex values are properly set. For example, error conditions may include cases where more than one treeitem in a tree has a tabindex value greater than or equal to 0, where tabindex is not set on any treeitem, or where aria-activedescendant is not defined when the element with the role tree has a tabindex value of greater than or equal to 0.

1.5.2. Testing Practices and Tools

The accessibility of interactive content cannot be confirmed by static checks alone. Developers of interactive content should test for device-independent access to widgets and applications, and should verify accessibility API access to all content and changes during user interaction.

1.6. Assistive Technologies

Programmatic access to accessibility semantics is essential for assistive technologies. Most assistive technologies interact with user agents, like other applications, through a recognized accessibility API. Perceivable objects in the user interface are exposed to assistive technologies as accessible objects, defined by the accessibility API interfaces. To do this properly, accessibility information – role, states, properties as well as contextual information – needs to be accurately conveyed to the assistive technologies through the accessibility API. When a state change occurs, the user agent provides the appropriate event notification to the accessibility API. Contextual information, in many host languages like HTML, can be determined from the DOM itself as it provides a contextual tree hierarchy.

While some assistive technologies interact with these accessibility APIs, others may access the content directly from the DOM. These technologies can restructure, simplify, style, or reflow the content to help a different set of users. Common use cases for these types of adaptations may be the aging population, persons with cognitive impairments, or persons in environments that interfere with use of their tools. For example, the availability of regional navigational landmarks may allow for a mobile device adaptation that shows only portions of the content at any one time based on its semantics. This could reduce the amount of information the user needed to process at any one time. In other situations it may be appropriate to replace a custom user interface control with something that is easier to navigate with a keyboard, or touch screen device.

2. Using WAI-ARIA

Complex web applications become inaccessible when assistive technologies cannot determine the semantics behind portions of a document or when the user is unable to effectively navigate to all parts of it in a usable way (see the WAI-ARIA Primer [ARIA-PRIMER]). WAI-ARIA divides the semantics into roles (the type defining a user interface element) and states and properties supported by the roles.

Authors need to associate elements in the document to a WAI-ARIA role and the appropriate states and properties (aria-* attributes) during its life-cycle, unless the elements already have the appropriate implicit WAI-ARIA semantics for states and properties. In these instances the equivalent host language states and properties take precedence to avoid a conflict while the role attribute will take precedence over the implicit role of the host language element.

2.2. WAI-ARIA States and Properties

WAI-ARIA provides a collection of accessibility states and properties which are used to support platform accessibility APIs on various operating system platforms. Assistive technologies may access this information through an exposed user agent DOM or through a mapping to the platform accessibility API. When combined with roles, the user agent can supply the assistive technologies with user interface information to convey to the user at any time. Changes in states or properties will result in a notification to assistive technologies, which could alert the user that a change has occurred.

In the following example, a list item (html:li) has been used to create a checkable menu item, and JavaScript events will capture mouse and keyboard events to toggle value of aria-checked. A role is used to make the behavior of this simple widget known to the user agent. Attributes that change with user actions (such as aria-checked) are defined in the states and properties section.

<li role="menuitemcheckbox" aria-checked="true">Sort by Last Modified</li>

Some accessibility states, called managed states, are controlled by the user agent. Examples of managed state include keyboard focus and selection. Managed states often have corresponding CSS pseudo-classes (such as :focus and ::selection) to define style changes. In contrast, the states in this specification are typically controlled by the author and are called unmanaged states. Some states are managed by the user agent, such as aria-posinset and aria-setsize, but the author can override them if the DOM is incomplete and would cause the user agent calculation to be incorrect. User agents map both managed and unmanaged states to the platform accessibility APIs.

Most modern user agents support CSS attribute selectors ([CSS]), and can allow the author to create UI changes based on WAI-ARIA attribute information, reducing the amount of scripts necessary to achieve equivalent functionality. In the following example, a CSS selector is used to determine whether or not the text is bold and an image of a check mark is shown, based on the value of the aria-checked attribute.

If CSS is not used to toggle the visual representation of the check mark, the author could include additional markup and scripts to manage an image that represents whether or not the menuitemcheckbox is checked.

2.3. Managing Focus

An application should always have an element with focus when in use, as applications require users to have a place to provide user input. Authors are advised to not destroy the element with focus or scroll it off-screen unless through user intervention. All interactive objects should be focusable. All parts of composite interactive controls need to be focusable or have a documented alternative method to achieve their function, such as a keyboard shortcut. Authors are advised to maintain an obvious, discoverable way, either through tabbing or other standard navigation techniques, for keyboard users to move the focus to any interactive element. See User Agent Accessibility Guidelines, Guideline 9 ([UAAG], Guideline 9).

When using standard HTML and basic WAI-ARIAwidgets, application developers can simply manipulate the tab order or use a script to create keyboard shortcuts to elements in the document. Use of more complex widgets requires the author to manage focus within them. SVG Tiny provides a similar navigation "ring" mechanism that by default follows document order and which should be implemented using system dependent input facilities (the TAB key on most desktop computers). SVG authors may place elements in the navigation order by manipulating the focusable attribute and they may dynamically specify the navigation order by modifying elements navigation attributes.

WAI-ARIA includes a number of "managing container" widgets, also known as "composite" widgets. When appropriate, the container is responsible for tracking the last descendant which was active (the default is usually the first item in the container). It is essential that a container maintain a usable and consistent strategy when focus leaves a container and is then later refocused. While there may be exceptions, it is recommended that when a previously focused container is refocused, the active descendant be the same element as the active descendant when the container was last focused. Exceptions include cases where the contents of a container widget have changed, and widgets like a menubar where the user expects to always return to the first item when focus leaves the menu bar. For example, if the second item of a tree group was the active descendant when the user tabbed out of the tree group, then the second item of the tree group remains the active descendant when the tree group gets focus again. The user may also activate the container by clicking on one of the descendants within it.

When the container or its active descendant has focus, the user may navigate through the container by pressing additional keys, such as the arrow keys, to change the currently active descendant. Any additional press of the main navigation key (generally the TAB key) will move out of the container to the next widget.

3. Normative Requirements for WAI-ARIA

This specification indicates whether a section is normative or informative. Classifying a section as normative or informative applies to the entire section. A statement "This section is normative" or "This section is informative" applies to all sub-sections of that section.

Normative sections provide requirements that authors, user agents, and assistive technologies MUST follow for an implementation to conform to this specification. The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, RECOMMENDED, MAY, and OPTIONAL in this document are to be interpreted as described in Keywords for use in RFCs to indicate requirement levels [RFC2119]. RFC-2119 keywords are formatted in uppercase and contained in a strong element with class="rfc2119". When the keywords shown above are used, but do not share this format, they do not convey formal information in the RFC 2119 sense, and are merely explanatory, i.e., informative. As much as possible, such usages are avoided in this specification.

Informative sections provide information useful to understanding the specification. Such sections may contain examples of recommended practice, but it is not required to follow such recommendations in order to conform to this specification.

The accessible name is the name of a user interface element. Each platform accessibility API provides
the accessible name property. The value of the accessible name may be
derived from a visible (e.g., the visible text on a button) or invisible
(e.g., the text alternative that describes an icon) property of the user
interface element.

A simple use for the accessible name property may be illustrated by
an "OK" button. The text "OK" is the accessible name.
When the button receives focus, assistive technologies may concatenate
the platform's role description with the accessible name. For example,
a screen reader may speak "push-button OK" or "OK button".
The order of concatenation and specifics of the role description (e.g. "button", "push-button", "clickable
button") are determined by platform accessibility APIs or assistive
technologies.

Assistive Technologies

Hardware and/or software that:

relies on services provided by a user agent to retrieve and render Web content

works with a user agent or web content itself through the use of APIs, and

provides services beyond those offered by the user agent to facilitate user interaction with web content by people with disabilities

This definition may differ from that used in other documents.

Examples of assistive technologies that are important in the context
of this document include the following:

screen magnifiers, which are used to enlarge and improve the visual
readability of rendered text and images;

screen readers, which are most-often used to convey information through
synthesized speech or a refreshable Braille display;

text-to-speech software, which is used to convert text into synthetic
speech;

speech recognition software, which is used to allow spoken control
and dictation;

alternate input technologies (including head pointers, on-screen
keyboards, single switches, and sip/puff devices), which are used to
simulate the keyboard;

alternate pointing devices, which are used to simulate mouse pointing
and clicking.

Attribute

In this specification, attribute is used as it is in markup languages.
Attributes are structural features added to elements to
provide information about the states and properties of
the object represented by the
element.

In this specification, element is used as it is in markup languages.
Elements are the structural elements in markup language that contains
the data profile for objects.

Event

A programmatic message used to communicate discrete changes in the state of
an object to other objects
in a computational system. User input to a web page is commonly mediated
through abstract events that describe the interaction and can provide
notice of changes to the state of a document object. In some programming
languages, events are more commonly known as notifications.

Hidden

Indicates that the element is
not visible or perceivable to any user.
An element is only considered hidden in the DOM if it or one
of its ancestor elements has the aria-hidden attribute
set to true.

Note: Authors are reminded that visibility:hidden and display:none apply to allCSS media types; therefore, use of either will hide the content from assistive technologies that access the DOM through a rendering engine. However, in order to support assistive technologies that access the DOM directly, or other authoring techniques to visibly hide content (for example, opacity or off-screen positioning), authors need to ensure the aria-hidden attribute is always updated accordingly when an element is shown or hidden, unless the intent of using off-screen positioning is to make the content visible only to screen reader users and not others.

Informative

Content provided for information purposes and not required for conformance.
Content required for conformance is referred to as normative.

A type of region on a page to which the user may want quick access.
Content in such a region is different from that of other regions on the
page and relevant to a specific user purpose, such as navigating, searching,
perusing the primary content, etc.

Live Region

Live regions are perceivable regions of a web page that are typically
updated as a result of an external event when user focus may be elsewhere.
These regions are not always updated as result of a user interaction.
This practice has become commonplace with the growing use of Ajax.
Examples of live regions include a chat log, stock ticker, or a sport scoring
section that updates periodically to reflect game statistics. Since these
asynchronous areas are expected to update outside the user's area of
focus, assistive technologies such as screen readers have either been
unaware of their existence or unable to process them for the user. WAI-ARIA
has provided a collection of properties that allow the author to identify
these live regions and how to process them: aria-live, aria-relevant,
aria-atomic, and aria-busy. Pre-defined live region roles are listed
in the Choosing
Between Special Case Live Regions ([ARIA-PRACTICES],
Section 5.3).

Primary Content Element

An implementing host language's primary content element, such as the body element in HTML.

Managed State

Accessibility APIstate that is controlled by the user agent, such as focus and selection. These are contrasted with "unmanaged states" that are typically controlled by the author. Nevertheless, authors can override some managed states, such as aria-posinset and aria-setsize. Many managed states have corresponding CSS pseudo-classes, such as :focus, and pseudo-elements, such as ::selection, that are also updated by the user agent.

Normative

Required for conformance. By contrast, content identified as informative or "non-normative" is
not required for conformance.

Object

In the context of user interfaces, an item in the perceptual user experience, represented in markup languages by one or more elements,
and rendered by user agents.

In the context of programming, the instantiation of one or more classes and interfaces which define the general characteristics of similar objects. An object in an accessibility API may represent one or more DOM objects. Accessibility APIs have defined interfaces that are distinct from DOM interfaces.

Ontology

A description of the characteristics of classes and
how they relate to each other.

A connection between two distinct things. Relationships
may be of various types to indicate which object labels
another, controls another, etc.

Role

Main indicator of type.
This semantic association
allows tools to present and support interaction with the object in a
manner that is consistent with user expectations about other objects
of that type.

Semantics

The meaning of something as understood by a human, defined in a way
that computers can process a representation of an object,
such as elements and attributes,
and reliably represent the object in a way that various humans will achieve
a mutually consistent understanding of the object.

State

A state is a dynamic property expressing
characteristics of an object that
may change in response to user action or automated processes. States
do not affect the essential nature of the object, but represent data
associated with the object or user interaction possibilities. See clarification
of states versus properties.

Taxonomy

A hierarchical definition of how the characteristics of various classes relate
to each other, in which classes inherit the properties of superclasses
in the hierarchy. A taxonomy can comprise part of the formal definition
of an ontology.

Any software that retrieves, renders and facilitates end user interaction with Web content. This definition may differ from that used in other documents.

Value

A literal that solidifies the information expressed by a state, property, role,
or text content.

acrWidget

Discrete user interface object with which the user can interact. Widgets
range from simple objects that have one value or operation (e.g., check
boxes and menu items), to complex objects that contain many managed sub-objects
(e.g., trees and grids).

5. The Roles Model

This section defines the WAI-ARIAroletaxonomy and describes the characteristics and properties of all roles. A formal RDF/OWL representation of all the information presented here is available in Schemata Appendix.

The roles, their characteristics, the states and properties they support, and specification of how they may be used in markup, shall be considered normative. The RDF/OWL representation used to model the taxonomy shall be considered informative. The RDF/OWL taxonomy may be used as a vehicle to extend WAI-ARIA in the future or by tool manufacturers to validate states and properties applicable to roles per this specification.

Roles are element types and authors MUST NOT change role values over time or with user actions. Authors wishing to change a role MUST do so by deleting the associated element and its children and replacing it with a new element with the appropriate role. Typically, platform accessibility APIs do not provide a vehicle to notify assistive technologies of a role value change, and consequently, assistive technologies may not update their cache with the new role attribute value.

In order to reflect the content in the DOM, user agents SHOULD map the role attribute to the appropriate value in the implemented accessibility API, and user agents SHOULD update the mapping when the role attribute changes.

5.1. Relationships Between Concepts

5.1.1. Superclass Role

Inheritance is expressed in RDF using the RDF Schema subClassOf ([RDFS]) property.

RDF Property

rdfs:subClassOf

The role that the current subclassed role extends in the taxonomy. This extension causes all the properties and constraints of the superclass role to propagate to the subclass role. Other than well known stable specifications, inheritance may be restricted to items defined inside this specification, so that external items cannot be changed and affect inherited classes.

5.1.3. Related Concepts

Informative data about a similar or related idea from other specifications. Concepts that are related are not necessarily identical. Related concepts do not inherit properties from each other. Hence if the definition of one concept changes, the properties, behavior, and definition of its related concept is not affected.

For example, a progress bar is like a status indicator. Therefore, the progressbarwidget has a role:relatedConcept value which includes status. However, if the definition of status is modified, the definition of a progressbar is not affected.

5.1.4. Base Concept

Informative data about objects that are considered prototypes for the role. Base concept is similar to type, but without inheritance of limitations and properties. Base concepts are designed as a substitute for inheritance for external concepts. A base concept is like a related concept except that the base concept is almost identical to the role definition.

For example, the checkbox defined in this document has similar functionality and anticipated behavior to a checkbox defined in HTML. Therefore, a checkbox has an HTMLcheckbox as a baseConcept. However, if the original HTML checkbox baseConcept definition is modified, the definition of a checkbox in this document will not be affected, because there is no actual inheritance of the respective type.

5.2. Characteristics of Roles

Roles are defined and described by their characteristics. Characteristics define the structural function of a role, such as what a role is, concepts behind it, and what instances the role can or must contain. In the case of widgets this also includes how it interacts with the user agent based on mapping to HTML forms and XForms. States and properties from WAI-ARIA that are supported by the role are also indicated.

The roles taxonomy defines the following characteristics. These characteristics are implemented in RDF as properties of the OWL classes that describe the roles.

5.2.1. Abstract Roles

Abstract roles are the foundation upon which all other WAI-ARIA roles are built. Content authors MUST NOT use abstract roles because they are not implemented in the API binding. User agents MUST NOT map abstract roles to the standard role mechanism of the accessibility API. Abstract roles are provided to help with the following:

Organize the role taxonomy and provide roles with a meaning in the context of known concepts.

5.2.2. Required States and Properties

States and properties specifically required for the role and subclass roles. Content authors MUST provide values for required states and properties.

When an object inherits from multiple ancestors and one ancestor indicates that property is supported while another ancestor indicates that it is required, the property is required in the inheriting object.

5.2.3. Supported States and Properties

States and properties specifically applicable to the role and child roles. User agentsMUST map all supported states and properties for the role to an accessibility API. Content authors MAY provide values for supported states and properties, but need not in some cases where default values are sufficient.

5.2.4. Inherited States and Properties

Informative list of properties that are inherited onto a role from superclass roles. States and properties are inherited from superclass roles in the role taxonomy, not from ancestor elements in the DOM tree. These properties are not explicitly defined on the role, as the inheritance of properties is automatic. This information is provided to facilitate reading of the specification. The set of supported states and properties combined with inherited states and properties forms the full set of states and properties supported by the role.

5.2.5. Required Owned Elements

Any element that will be owned by the element with this role. For example, an element with the role list will own at least one element with the role group or listitem.

When multiple roles are specified as required owned elements for a role, at least one instance of one required owned element is expected. This specification does not require an instance of each of the listed owned roles. For example, a menu should have at least one instance of a menuitem, menuitemcheckbox, ormenuitemradio. The menu role does not require one instance of each.

There may be times that required owned elements are missing, for example, while editing or while loading a data set. When a widget is missing required owned elements due to script execution or loading, authors MUST mark a containing element with aria-busy equal to true. For example, until a page is fully initialized and complete, an author could mark the document element as busy.

Note: A role that has 'required owned elements' does not imply the reverse relationship. While processing of a role may be incomplete without elements of given roles present as descendants, elements with roles in this list do not always have to be found within elements of the given role. See required context role for requirements about the context where elements of a given role will be contained.

Note: An element with a subclass role of the 'required owned element' does not fulfill this requirement. For example, the list role requires ownership of an element using either the listitem or group role. Although the group role is the superclass of row, adding a owned element with a role of row will not fulfill the requirement that list must own a listitem or a group.

5.2.6. Required Context Role

The required context role defines the owning container where this role is allowed. If a role has a required context, authors MUST ensure that an element with the role is contained inside (or owned by) an element with the required context role. For example, an element with role listitem is only meaningful when contained inside (or owned by) an element with role list.

Note: A role that has 'required context role' does not imply the reverse relationship. While an element with the given role needs to appear within an element of the listed role(s) in order to be meaningful, elements of the listed roles do not always need descendant elements of the given role in order to be meaningful. See required owned elements for requirements about elements that require presence of a given descendant to be processed properly.

5.2.7. Accessible Name Calculation

author: name comes from values provided by the author in explicit markup features such as the aria-label attribute, aria-labelledby attribute, or the host language labeling mechanism, such as the alt or title attributes in HTML, with HTML title attribute having the lowest precedence for specifying a text alternative.

contents: name comes from the text value of the element node. Although this may be allowed in addition to "author" in some roles, this is used in content only if higher priority "author" features are not provided. Note: Priority is defined by the text alternative computation algorithm.

5.2.7.1. Name Computation

5.2.7.2. Description Computation

An accessible description may be computed by concatenating the text alternatives for nodes referenced by an aria-describedby attribute on the current node. The text alternatives for the referenced nodes are computed using a number of methods, outlined below in the section titled Text Alternative Computation.

5.2.7.3. Text Alternative Computation

The text equivalent computation outlined below is a description of how user agents acquire a name or description that they then publish through the accessibility API. Authors can use the current section as a guide for creating names and descriptions in their markup. Accessibility checker tools can implement a name and/or description generator based on this algorithm such that authors can use the generated text equivalent to confirm that names and descriptions are as the author intended.

The text alternative is reused in both the name and description computation, as described above. There are different rules provided for several different types of nodes and combinations of markup. Text alternatives are built up, when appropriate, from all the relevant content contained within an element. This is accomplished via rule 2C (which is recursive), using the full set of rules to retrieve text from its own children.

The text alternative for a given node is computed as follows:

Skip hidden elements unless the author specifies to use them via an aria-labelledby or aria-describedby being used in the current computation. By default, users of assistive technologies won't receive the hidden information, but an author will be able to explicitly override that and include the hidden text alternative as part of the label string sent to the accessibility API.

For any non-skipped elements:

Authors MAY specify an element's text alternative in content attributes, used in this order of preference:

The aria-labelledby attribute takes precedence as the element's text alternative unless this computation is already occurring as the result of a recursive aria-labelledby declaration (in other words, aria-labelledby is not recursive when referenced from another element, so it will not cause loops). However, the element's aria-labelledby attribute can reference the element's own IDREF in order to concatentate a string provided by the element's aria-label attribute or another feature lower in this preference list. The text alternatives for all the elements referenced will be computed using this same set of rules. User agents will then trim whitespace and join the substrings using a single space character. Substrings will be joined in the order specified by the author (IDREF order in the aria-labelledby attribute).

If aria-labelledby is empty or undefined, the aria-label attribute, which defines an explicit text string, is used. However, if this computation is already occurring as the result of a recursive text alternative computation and the current element is an embedded control as defined in rule 2B, ignore the aria-label attribute and skip directly to rule 2B.

If aria-labelledby and aria-label are both empty or undefined, and if the element is not marked as presentational (role="presentation"), check for the presence of an equivalent host language attribute or element for associating a label, and use those mechanisms to determine a text alternative. For example, in HTML, the img element's alt attribute defines a label string and the label element references the form element it labels. See How to Specify Alternate Text ([HTML], section 13.8) and HTML 5 Requirements for providing text to act as an alternative for images ([HTML5], section 4.8.1.1).

Editorial Note: We've asked the HTML5 WG to remove or reduce this section, so we may remove the reference to it from ARIA.

Authors sometimes embed a control within the label of another widget, where the user can adjust the embedded control's value. For example, consider a check box label that contains a text input field: "Flash the screen [input] times". If the user has entered "5" for the embedded text input, the complete label is "Flash the screen 5 times". For such cases, include the value of the embedded control as part of the text alternative in the following manner:

If the embedded control is a text field, use its value.

If the embedded control is a menu, use the text alternative of the chosen menu item.

If the embedded control is a select or combobox, use the chosen option.

If the embedded control is a range (e.g., a spinbutton or slider), use the value of the aria-valuetext attribute if available, or otherwise the value of the aria-valuenow attribute.

Otherwise, if the attributes checked in rules A and B didn't provide results, text is collected from descendant content if the current element's role allows "Name From: contents." The text alternatives for child nodes will be concatenated, using this same set of rules. This same rule may apply to a child, which means the computation becomes recursive and can result in text being collected in all the nodes in this subtree, no matter how deep they are. However, any given descendant subtree may instead collect their part of the text alternative from the preferred markup described in A and B above. These author-specified attributes are assumed to provide the correct text alternative for the entire subtree. All in all, the node rules are applied consistently as text alternatives are collected from descendants, and each containing element in those descendants may or may not allow their contents to be used. Each node in the subtree is consulted only once. If text has been collected from a child node, and is referenced by another IDREF in some descendant node, then that second, or subsequent, reference is not followed. This is done to avoid infinite loops.

The last resort is to use text from a tooltip attribute (such as the title attribute in HTML). This is used only if nothing else, including subtree content, has provided results.

Text nodes are often visited because they are children of an element that uses rule 2C to collect text from its children. However, because it is possible to specify or alter textual content using CSS rules, it is necessary for user agents to combine such content, as appropriate, with the text referenced by the text nodes to produce a complete text alternative. An example is the use of CSS:before and :after pseudo-elements, where the user agent combines the textual content specified in the style sheet with that given in the DOM.

When an image replaces text, then the UA should use the original text, since that text is presumably the equivalent.

When text replaces an image, then the UA should provide that text.

When new text replaces old, then the UA should include the new text, since that is what is rendered on screen.

Note: Though the user agent may make efforts to compute a text alternative from CSS-generated text in the absence of text content determinable from the DOM, authors should not provide text through a style sheet, as the user agent may incorrectly determine the text alternative.

The purpose of the flat text alternative string is to create a perceivable label in alternative presentations. At each step of the algorithm, an implementation will trim the existing text equivalent string and the string to be added, then join those two strings with a single space. For example, a space character may be inserted between the text of two elements used one after the other in a description.

5.2.7.4. Text Alternative Computation Example #1

aria-labelledby (Rule 2A): The label of the first menuitem in the menubar example markup above is "File" based on rule 2A. The element has an aria-labelledby attribute that picks out the span element with id="fileLabel" The span contains the label text.

Namefrom: contents (Rule 2C): The label of the first item in the file menu is "New" based on rule 2C. Since menuitem elements can acquire their label by the "Namefrom: content" technique, the textual content of the menuitem element itself is sufficient. Note that this element has no attributes such as aria-labelledby, aria-label, or alt, from which to acquire a label.

5.2.7.5. Text Alternative Computation Example #2

native label element (Rule 2A): Use of a native element is illustrated by the first checkbox where its label is defined by the HTML label element.

embedded input (Rule 2C): The third checkbox illustrates an embedded control adding to a larger label (Rule 2B). Here the label is "Flash the screen 3 times", where "3" is taken from the value of the embedded text input.

aria-label (Rule 2A): Rule 2A, using aria-label, is shown for this embedded text input. The rationale is to give a label to this element, but in a way that does not interfere with the enclosing label of the checkbox. The label is needed by a screen reader when focus is on the text input.

5.2.9. Implicit Value for Role

Many states and properties have default values. Occasionally, the default value when used on a given role should be different from the usual default. Roles that require a state or property to have a non-standard default value indicate this in the "Implicit Value for Role". This is expressed in the form "state or property name is new default value". Roles that define this have the new default value for the state or property if the author does not provide an explicit value.

5.3. Categorization of Roles

To support the current user scenario, this specification categorizes roles that define user interface widgets (sliders, tree controls, etc.) and those that define page structure (sections, navigation, etc.). Note that some assistive technologies provide special modes of interaction for regions marked with role application or document.

5.3.4. Landmark Roles

The following roles are regions of the page intended as navigational landmarks. All of these roles inherit from the landmark base type and, with the exception of application, all are imported from the Role Attribute [ROLE]. The roles are included here in order to make them clearly part of the WAI-ARIA Role taxonomy.

A dialog is an application window that is designed to interrupt the current processing of an application in order to prompt the user to enter information or require a response. See related alertdialog.

A large perceivable section of a web page or document, that is important enough to be included in a page summary or table of contents, for example, an area of the page containing live sporting event statistics.

alert(role)

A message with important, and usually time-sensitive, information. See related alertdialog and status.

Alerts are used to convey messages to alert the user. In the case of audio warnings this is an accessible alternative for a hearing-impaired user. The alertrole goes on the node containing the alert message. Alerts are specialized forms of the status role, which will be processed as an atomic live region.

Alerts are assertive live regions and will be processed as such by assistive technologies. Neither authors nor user agents are required to set or manage focus to them in order for them to be processed. Since alerts are not required to receive focus, content authors SHOULD NOT require users to close an alert. If the operating system allows, the user agentSHOULD fire a system alert event through the accessibility API when the WAI-ARIA alert is created. If an alert requires focus to close the alert, then content authors SHOULD use alertdialog instead.

Note: Elements with the role alert have an implicit aria-live value of assertive, and an implicit aria-atomic value of true.

alertdialog(role)

A type of dialog that contains an alert message, where initial focus goes to an element within the dialog. See related alert and dialog.

Alert dialogs are used to convey messages to alert the user. The alertdialogrole goes on the node containing both the alert message and the rest of the dialog. Content authors SHOULD make alert dialogs modal by ensuring that, while the alertdialog is shown, keyboard and mouse interactions only operate within the dialog.

Unlike alert, alertdialog can receive a response from the user. For example, to confirm that the user understands the alert being generated. When the alert dialog is displayed, authors SHOULD set focus to an active element within the alert dialog, such as a form edit field or an OK button. The user agentSHOULD fire a system alert event through the accessibility API when the alert is created, provided one is specified by the intended accessibility API.

Authors SHOULD use aria-describedby on an alertdialog to point to the alert message element in the dialog. If they do not, assistive technologies will resort to their internal recovery mechanism to determine the contents of an alert message.

application(role)

When the user navigates an element assigned the role of application, assistive technologies that typically intercept standard keyboard events SHOULD switch to an application browsing mode, and pass keyboard events through to the web application. The intent is to hint to certain assistive technologies to switch from normal browsing mode into a mode more appropriate for interacting with a web application; some user agents have a browse navigation mode where keys, such as up and down arrows, are used to browse the document, and this native behavior prevents the use of these keys by a web application.

Note: Where appropriate, assistive technologies that typically intercept other standard device input events, such as touch screen input, could switch to an application browsing mode that passes some or all of those events through to the web application.

Authors SHOULD set the role of application on the element that encompasses the entire application. If the application role applies to the entire web page, authors SHOULD set the role of application on the root node for content, such as the body element in HTML or svg element in SVG.

For example, an email application has a document and an application in it. The author would want to use typical application navigation mode to cycle through the list of emails, and much of this navigation would be defined by the application author. However, when reading an email message the content will appear in a region with a documentrole in order to use browsing navigation.

Authors SHOULD provide a title or label for applications. Authors SHOULD use label text that is suitable for use as a navigation preview or table-of-contents entry for the page section. Content authors SHOULD provide the label through one of the following methods:

If the application includes the entire contents of the web page, use the host language feature for title or label, such as the title element in both HTML and SVG. This has the effect of labeling the entire application.

Otherwise, provide a visible label referenced by the application using aria-labelledby.

User agents SHOULD treat elements with the role of application as navigational landmarks.

Authors MAY use the application role on the primary content element of the host language (such as the body element in HTML) to define an entire page as an application. However, if the primary content element is defined as having a role of application, user agents MUST NOT use the element as a navigational landmark. If assistive technologies use an interaction mode that intercepts standard keyboard events, when encountering the application role, those assistive technologies SHOULD switch to an interaction mode that passes keyboard events through to the web application.

article(role)

A section of a page that consists of a composition that forms an independent part of a document, page, or site.

An article is not a navigational landmark, but may be nested to form a discussion where assistive technologies could pay attention to article nesting to assist the user in following the discussion. An article could be a forum post, a magazine or newspaper article, a web log entry, a user-submitted comment, or any other independent item of content. It is independent in that its contents could stand alone, for example in syndication. However, the element is still associated with its ancestors; for instance, contact information that applies to a parent body element still covers the article as well. When nesting articles, the child articles represent content that is related to the content of the parent article. For instance, a web log entry on a site that accepts user-submitted comments could represent the comments as articles nested within the article for the web log entry. Author, heading, date, or other information associated with an article does not apply to nested articles.

When the user navigates an element assigned the role of article, assistive technologies that typically intercept standard keyboard events SHOULD switch to document browsing mode, as opposed to passing keyboard events through to the web application. Assistive technologies MAY provide a feature allowing the user to navigate the hierarchy of any nested article elements.

banner(role)

A region that contains mostly site-oriented content, rather than page-specific content.

Site-oriented content typically includes things such as the logo or identity of the site sponsor, and site-specific search tool. A banner usually appears at the top of the page and typically spans the full width.

User agents SHOULD treat elements with the role of banner as navigational landmarks.

Note: Because document and application elements can be nested in the DOM, they may have multiple banner elements as DOM descendants, assuming each of those is associated with different document nodes, either by a DOM nesting (e.g., document within document) or by use of the aria-ownsattribute.

checkbox(role)

A checkable input that has three possible values: true, false, or mixed.

The aria-checkedattribute of a checkbox indicates whether the input is checked (true), unchecked (false), or represents a group of elements that have a mixture of checked and unchecked values (mixed). Many checkboxes do not use the mixed value, and thus are effectively boolean checkboxes.

columnheader(role)

columnheader can be used as a column header in a table or grid. It could also be used in a pie chart to show a similar relationship in the data.

The columnheader establishes a relationship between it and all cells in the corresponding column. It is the structural equivalent to an HTMLthelement with a column scope.

Authors MUST ensure elements with rolecolumnheader are contained in, or owned by, an element with the role row.

Note: Because cells are organized into rows, there is not a single container element for the column. The column is the set of gridcell elements in a particular position within their respective row containers.

combobox(role)

A presentation of a select; usually similar to a textbox where users can type ahead to select an option, or type to enter arbitrary text as a new item in the list. See related listbox.

combobox is the combined presentation of a single line textfield with a listbox popup. The combobox may be editable. Typically editable combo boxes are used for autocomplete behavior, and authors SHOULD set aria-autocomplete attribute on the textfield.

If an author sets a combobox's value of aria-autocomplete to 'none' (default), authors MUST manage and set focus on the associated listbox, so assistive technologies can follow the currently selected value.

If an author sets a combobox's value of aria-autocomplete to 'inline' or 'both', authors MUST update the value of the focused textfield, so assistive technologies can announce the currently selected value.

If an author sets a combobox's value of aria-autocomplete to 'list', user agents MUST expose changes to the aria-activedescendant attribute on the combobox while the combobox remains focused. If a change to the aria-activedescendant attribute occurs while the combobox is focused, assistive technologies SHOULD alert the user of that change, for example, by speaking the text alternative of the new active descendant element. Authors SHOULD associate the combobox textfield with its listbox using aria-owns. For example:

Note: In XForms [XFORMS] the same select can have one of 3 appearances: combo-box, drop-down box, or group of radio-buttons. Many browsers allow users to type ahead to existing choices in a drop-down select widget. This specification does not constrain the presentation of the combo box.

complementary(role)

A supporting section of the document, designed to be complementary to the main content at a similar level in the DOM hierarchy, but remains meaningful when separated from the main content.

There are various types of content that would appropriately have this role. For example, in the case of a portal, this may include but not be limited to show times, current weather, related articles, or stocks to watch. The complementary role indicates that contained content is relevant to the main content. If the complementary content is completely separable main content, it may be appropriate to use a more general role.

User agents SHOULD treat elements with the role of complementary as navigational landmarks.

composite(abstract role)

Authors SHOULD ensure that a composite widget exist as a single navigation stop within the larger navigation system of the web page. Once the composite widget has focus, authors SHOULD provide a separate navigation mechanism for users to navigate to elements that are descendants or owned children of the composite element.

Note: composite is an abstract role used for the ontology. Authors are instructed not to use this role in content.

Note: Because document and application elements can be nested in the DOM, they may have multiple contentinfo elements as DOM descendants, assuming each of those is associated with different document nodes, either by a DOM nesting (e.g., document within document) or by use of the aria-owns attribute.

definition(role)

The WAI-ARIA specification does not provide a role to specify the definition term, but host languages may provide such an element. If a host language has an appropriate element for the term (e.g., dfn or dt in HTML), authors SHOULD include the term in that element. Authors SHOULD identify the definition term by using an aria-labelledbyattribute on each element with a role of definition.

dialog(role)

A dialog is an application window that is designed to interrupt the current processing of an application in order to prompt the user to enter information or require a response. See related alertdialog.

Authors SHOULD provide a dialog label. Labels may be provided with the aria-label or aria-labelledbyattribute if other mechanisms are not available. Authors SHOULD ensure each active dialog has a focused descendant element that has keyboard focus.

directory(role)

A list of references to members of a group, such as a static table of contents.

Authors SHOULD use this role for a static table of contents, whether linked or unlinked. This includes tables of contents built with lists, including nested lists. Dynamic tables of contents, however, might use a tree role instead.

document(role)

A region containing related information that is declared as document content, as opposed to a web application.

When the user navigates an element assigned the role of document, assistive technologies that typically intercept standard keyboard events SHOULD switch to document browsing mode, as opposed to passing keyboard events through to the web application. The documentrole informs user agents of the need to augment browser keyboard support in order to allow users to visit and read any content within the document region. In contrast, additional commands are not necessary for screen reader users to read text within a region with the application role, where if coded in an accessible manner, all text will be semantically associated with focusable elements. An important trait of documents is that they have text which is not associated with widgets or groups thereof.

Authors SHOULD set the role of document on the element that encompasses the entire document. If the document role applies to the entire web page, authors SHOULD set the role of document on the root node for content, such as the body element in HTML or svg element in SVG.

For example, an email application has a document and an application in it. The author would want to use typical application navigation mode to cycle through the list of emails, and much of this navigation would be defined by the application author. However, when reading an email message, the content will appear in a region with a document role in order to use browsing navigation.

Authors SHOULD provide a title or label for documents. Authors SHOULD use label text that suitable for use as a navigation preview or table-of-contents entry for the page section. Content authors SHOULD provide the label through one of the following methods:

If the document includes the entire contents of the web page, use the host language feature for title or label, such as the title element in both HTML and SVG. This has the effect of labeling the entire document.

Otherwise, provide a visible label referenced by the document using aria-labelledby.

form(role)

A landmark region that contains a collection of items and objects that, as a whole, combine to create a form. See related search.

A form may be a mix of host language form controls, scripted controls, and hyperlinks. Authors are reminded to use native host language semantics to create form controls, whenever possible. For search facilities, authors SHOULD use the search role and not the generic form role. Authors SHOULD provide a visible label for the form referenced with aria-labelledby. If an author uses a script to submit a form based on a user action that would otherwise not trigger an onsubmit event (for example, a form submission triggered by the user changing a form element's value), the author SHOULD provide the user with advance notification of the behavior. Authors are reminded to use native host language semantics to create form controls, whenever possible.

User agents SHOULD treat elements with the role of form as navigational landmarks.

grid(role)

A grid is an interactive control which contains cells of tabular data arranged in rows and columns, like a table.

Grids do not necessarily imply presentation. The grid construct describes relationships between data such that it may be used for different presentations. Grids allow the user to move focus between cells using two dimensional navigation. For example, grid might be used as the invisible data model (hidden with CSS but still operable by assistive technologies) for a presentational chart.

Authors MUST ensure that elements with role gridcell are owned by elements with role row, which in turn are owned by an element with role rowgroup, grid or treegrid. If the author applies any non-global WAI-ARIA states or properties to a native markup element that is acting as a row (such as the tr element in HTML), the author MUST also apply the role of row, as stated in the section on Implementation in Host Languages. Authors MAY make cells focusable. Authors MAY provide row and column headers for grids, by using rowheader and columnheader roles.

Since WAI-ARIA can augment an element in the host language, grids can reuse existing functionality of native table grids. When WAI-ARIA grid or gridcell roles overlay host language table elements they reuse the host language semantics for that table. For instance, WAI-ARIA does not specify general attributes for gridcell elements that span multiple rows or columns. When the author needs a gridcell to span multiple rows or columns, use the host language markup, such as the colspan and rowspan attributes in HTML.

Authors MAY determine the contents of a gridcell through calculation of a mathematical formula. Authors MAY make a cell's formula editable by the user. In a spreadsheet application for example, the text alternative of a cell may be the calculated value of a formula. However, when the cell is being edited, the text alternative may be the formula itself.

gridcell elements with the aria-selectedattribute set can be selected for user interaction, and if the aria-multiselectable attribute of the grid is set to true, multiple cells in the grid may be selected. Grids may be used for spreadsheets like those in desktop spreadsheet applications.

A grid is considered editable unless otherwise specified. To make a grid read-only, set the aria-readonly attribute of the grid to true. The value of the grid element's aria-readonly attribute is implicitly propagated to all of its ownedgridcell elements, and will be exposed through the accessibility API. An author may override an individual gridcell element's propagated aria-readonly value by setting the aria-readonly attribute on the gridcell.

In a treegrid, authors MAY define cells as expandable by using the aria-expanded attribute. If the aria-expanded attribute is provided, it applies only to the individual cell. It is not a proxy for the container row, which also can be expanded. The main use case for providing this attribute on a cell is pivot table behavior.

Authors MUST ensure elements with rolegridcell are contained in, or owned by, an element with the role row.

group(role)

Contrast with region which is a grouping of user interface objects that will be included in a page summary or table of contents.

Authors SHOULD use a group to form logical collection of items in a widget such as children in a tree widget forming a collection of siblings in a hierarchy, or a collection of items having the same container in a directory. However, when a group is used in the context of list, authors MUST limit its children to listitem elements. Therefore, proper handling of group by authors and assistive technologies is determined by the context in which it is provided.

Authors MAY nest group elements. If a section is significant enough to warrant inclusion in the web page's table of contents, the author SHOULD assign the section a role of region or a standard landmark role.

img(role)

An img can contain captions and descriptive text, as well as multiple image files that when viewed together give the impression of a single image. An img represents a single graphic within a document, whether or not it is formed by a collection of drawing objects. In order for elements with a role of img be perceivable, authors MUST provide alternative text or a label determined by the accessible name calculation.

link(role)

An interactive reference to an internal or external resource that, when activated, causes the user agent to navigate to that resource. See related button.

If this is a native link in the host language (such as an HTML anchor with an hrefvalue), activating the link causes the user agent to navigate to that resource. If this is a simulated link, the web application author is responsible for managing navigation.

Note: If pressing the link triggers an action but does not change browser focus or page location, authors are advised to consider using the button role instead of the link role.

log(role)

A type of live region where new information is added in meaningful order and old information may disappear. See related marquee.

Examples include chat logs, messaging history, game log, or an error log. In contrast to other live regions, in this role there is a relationship between the arrival of new items in the log and the reading order. The log contains a meaningful sequence and new information is added only to the end of the log, not at arbitrary points.

Note: Elements with the role log have an implicit aria-live value of polite.

main(role)

This marks the content that is directly related to or expands upon the central topic of the document. The mainrole is a non-obtrusive alternative for "skip to main content" links, where the navigation option to go to the main content (or other landmarks) is provided by the user agent through a dialog or by assistive technologies.

User agents SHOULD treat elements with the role of main as navigational landmarks.

Note: Because document and application elements can be nested in the DOM, they may have multiple main elements as DOM descendants, assuming each of those is associated with different document nodes, either by a DOM nesting (e.g., document within document) or by use of the aria-owns attribute.

math(role)

Content with the role math is intended to be marked up in an accessible format such as MathML [MATHML], or with another type of textual representation such as TeX or LaTeX, which can be readily converted to an accessible format by assistive technologies.

This role provides a hook whereby a plug-in mechanism can provide multi-modal access to compliant MathML, as well as enabling support for MathML in "mainstream" user agents.

While it is inappropriate to use an image of a mathematical expression in the math role, there exists a significant amount of legacy content where images are used to represent mathematical expressions. For purposes of repair, if an image has been used to represent a mathematical expression, the text equivalent defined for that image SHOULD be valid MathML or TeX. Such images SHOULD also be labeled by text that describes the mathematical expression as it might be spoken, using the aria-describedby attribute.

menu(role)

A menu is often a list of common actions or functions that the user can invoke. The menurole is appropriate when a list of menu items is presented in a manner similar to a menu on a desktop application.

menubar(role)

A presentation of menu that usually remains visible and is usually presented horizontally.

The menubarrole is used to create a menu bar similar to those found in Windows, Mac, and Gnome desktop applications. A menu bar is used to create a consistent set of frequently used commands. Authors SHOULD ensure that menubar interaction is similar to the typical menu bar interaction in a desktop graphical user interface.

menuitem(role)

Authors MAY disable a menu item with the aria-disabled attribute. If the menu item has its aria-haspopup attribute set to true, it indicates that the menu item may be used to launch a sub-level menu, and authors SHOULD display a new sub-level menu when the menu item is activated.

Authors MUST ensure that menu items are owned by an element with role menu or menubar in order to identify that they are related widgets. Authors MAY separate menu items into sets by use of a separator or an element with an equivalent role from the native markup language.

menuitemcheckbox(role)

A menuitem with a checkable state whose possible values are true, false, or mixed.

The aria-checkedattribute of a menuitemcheckbox indicates whether the menu item is checked (true), unchecked (false), or represents a sub-level menu of other menu items that have a mixture of checked and unchecked values (mixed).

Authors MUST ensure that menu item checkboxes are owned by an element with role menu or menubar in order to identify that they are related widgets. Authors MAY separate menu items into sets by use of a separator or an element with an equivalent role from the native markup language.

menuitemradio(role)

A checkable menuitem in a set of elements with rolemenuitemradio, only one of which can be checked at a time.

Authors SHOULD enforce that only one menuitemradio in a group can be checked at the same time. When one item in the group is checked, the previously checked item becomes unchecked (its aria-checkedattribute becomes false).

Authors MUST ensure that menu item radios are owned by an element with role group, menu, or menubar in order to identify that they are related widgets. Authors MAY separate menu items into sets by use of a separator or an element with an equivalent role from the native markup language.

If a menu or menubar contains more than one group of menuitemradio elements, or if the menu contains one group and other, unrelated menu items, authors SHOULD nest each set of related menuitemradio elements in an element using the group role, and authors SHOULD delimit the group from other menu items with an element using the separator role.

presentation(role)

The intended use is when an element is used to change the look of the page but does not have all the functional, interactive, or structural relevance implied by the element type, or may be used to provide for an accessible fallback in older browsers that do not support WAI-ARIA.

An image that is in a container with the img role and where the full text alternative is available and is marked up with aria-labelledby and (if needed) aria-describedby;

An element used as an additional markup "hook" for CSS; or

A layout table and/or any of its associated rows, cells, etc.

For any element with a role of presentation and which is not focusable, the user agent MUST NOT expose the implicit native semantics of the element (the role and its states and properties) to accessibility APIs. However, the user agent MUST expose content and descendant elements that do not have an explicit or inherited role of presentation. Thus, the presentation role causes a given element to be treated as having no role or to be removed from the accessibility tree, but does not cause the content contained within the element to be removed from the accessibility tree.

For example, according to an accessibility API, the following markup elements would appear to have identical role semantics (no role) and identical content.

<!-- 1. [role="presentation"] negates the implicit 'heading' role semantics but does not affect the contents. --><h1 role="presentation"> Sample Content </h1><!-- 2. There is no implicit role for span, so only the contents are exposed. --><span> Sample Content </span><!-- 3. This role declaration is redundant. --><span role="presentation"> Sample Content </span><!-- 4. In all cases, the element contents are exposed to accessibility APIs without any implied role semantics. --><!-- <> --> Sample Content <!-- </> -->

The presentation role is used on an element that has implicit native semantics, meaning that there is a default accessibility API role for the element. Some elements are only complete when additional descendant elements are provided. For example, in HTML, table elements (matching the grid role) require tr descendants (the row role), which in turn require th or td children (the gridcell, columnheader, rowheader roles). Similarly, lists require list item children. The descendant elements that complete the semantics of an element are described in WAI-ARIA as required owned elements.

When an explicit or inherited role of presentation is applied to an element with the implicit semantic of a WAI-ARIA role that has required owned elements, in addition to the element with the explicit role of presentation, the user agent MUST apply an inherited role of presentation to any owned elements that do not have an explicit role defined. Also, when an explicit or inherited role of presentation is applied to a host language element which has required children as defined by the host language specification, in addition to the element with the explicit role of presentation, the user agent MUST apply an inherited role of presentation to any required children that do not have an explicit role defined. For any element with an explicit or inherited role of presentation and which is not focusable, user agents MUST ignore role-specific WAI-ARIA states and properties for that element. For example, in HTML, a ul or ol element with a role of presentation will have the implicit native semantics of its li elements removed because the list role to which the ul or ol corresponds has a required owned element of listitem. Likewise, although an HTMLtable element does not have an implicit native semantic role corresponding directly to a WAI-ARIA role, the implicit native semantics of its thead/tbody/tfoot/tr/th/td descendants will also be removed, because the HTML specification indicates that these are required structural descendants of the table element. Explicit roles on a descendant or owned element override the inherited role of presentation, and cause the owned element to behave as any other element with an explicit role. If the action of exposing the implicit role causes the accessibility tree to be malformed, the expected results are undefined and the user agent MAY resort to an internal recovery mechanism to repair the accessibility tree.

Note: Only the implicit native semantics of elements that correspond to WAI-ARIArequired owned elements are removed. All other content remains intact, including nested tables or lists, unless those elements also have a explicit role of presentation applied.

For example, according to an accessibility API, the following markup elements would appear to have identical role semantics (no roles) and identical content.

<!-- 1. [role="presentation"] negates the implicit 'list' and 'listitem' role semantics but does not affect the contents. --><ul role="presentation"><li> Sample Content </li><li> More Sample Content </li></ul><!-- 2. There is no implicit role for span, so only the contents are exposed. --><span><span> Sample Content </span><span> More Sample Content </span></span>

Note: There are other WAI-ARIA roles with required children for which this situation is applicable (e.g., radiogroups and listboxes), but tables and lists are the most common real-world cases in which the presentation inheritance is likely to apply.

For any element with an explicit or inherited role of presentation, user agents MUST apply an inherited role of presentation to all host-language-specific labeling elements for the presentational element. For example, a table element with a role of presentation will have the implicit native semantics of its caption element removed, because the caption is merely a label for the presentational table.

For any element with an explicit or inherited role of presentation, user agents MUST ignore any non-global, role-specific WAI-ARIA states and properties. However, the user agent MUST always expose global WAI-ARIA states and properties to accessibility APIs, even if an element has an explicit or inherited role of presentation.

For example, aria-hidden is a global attribute and would always be applied; aria-level is not a global attribute and would therefore only apply if the element was not in a presentational state.

If an element with a role of presentation is focusable, user agents MUST ignore the normal effect of the role and expose the element with implicit native semantics, in order to ensure that the element is both understandable and operable. Authors SHOULD NOT provide meaningful alternative text (for example, use alt="" in HTML4) when the presentation role is applied to an image.

In the following code sample, the containing div element has a WAI-ARIA role of img and is appropriately labeled by the caption paragraph. In this example the img element can be marked as presentation because the role and the text alternatives are provided by the containing element.

In the following code sample, because the anchor (HTMLa element) is acting as the treeitem, the list item (HTMLli element) is assigned an explicit WAI-ARIA role of presentation to override the user agent's implicit native semantics for list items.

progressbar(role)

An element that displays the progress status for tasks that take a long time.

A progressbar indicates that the user's request has been received and the application is making progress toward completing the requested action. The author SHOULD supply values for aria-valuenow, aria-valuemin, and aria-valuemax, unless the value is indeterminate, in which case the author SHOULD omit the aria-valuenow attribute. Authors SHOULD update these values when the visual progress indicator is updated. If the progressbar is describing the loading progress of a particular region of a page, the author SHOULD use aria-describedby to point to the status, and set the aria-busy attribute to true on the region until it is finished loading. It is not possible for the user to alter the value of a progressbar because it is always readonly.

Note: Assistive technologies generally will render the value of aria-valuenow as a percent of the range between the value of aria-valuemin and aria-valuemax, unless aria-valuetext is specified. It is best to set the values for aria-valuemin, aria-valuemax, and aria-valuenow in a manner that is appropriate for this calculation.

Note: Elements with the role progressbar have an implicit aria-readonly value of true.

radio(role)

A checkable input in a group of radioroles, only one of which can be checked at a time.

Authors SHOULD ensure that elements with role radio are explicitly grouped in order to indicate which ones affect the same value. This is achieved by enclosing the radio elements in an element with role radiogroup. If it is not possible to make the radio buttons DOM children of the radiogroup, authors SHOULD use the aria-ownsattribute on the radiogroup element to indicate the relationship to its children.

radiogroup(role)

A radiogroup is a type of select list that can only have a single entry checked at any one time. Authors SHOULD enforce that only one radio button in a group can be checked at the same time. When one item in the group is checked, the previously checked item becomes unchecked (its aria-checkedattribute becomes false).

region(role)

A large perceivable section of a web page or document, that is important enough to be included in a page summary or table of contents, for example, an area of the page containing live sporting event statistics.

The 'page summary' referenced above is a structure created dynamically from the page after it is loaded as a means of quickly describing its overall organization. It may be created by the author using a script, or by assistive technologies.

Authors SHOULD ensure that a region has a heading referenced by aria-labelledby. This heading is provided by an instance of the standard host language heading element or an instance of an element with role heading that contains the heading text.

When defining regions of a web page, authors are advised to consider using standard document landmarkroles. If the definitions of these regions are inadequate, authors can use the region role and provide the appropriate accessible name.

roletype(abstract role)

Properties of this role describe the structural and functional purpose of objects that are assigned this role (known in RDF terms as "instances"). A role is a concept that can be used to understand and operate instances.

Note: roletype is an abstract role used for the ontology. Authors are instructed not to use this role in content.

rowheader(role)

Rowheader can be used as a row header in a table or grid. The rowheader establishes a relationship between it and all cells in the corresponding row. It is a structural equivalent to setting scope="row" on an HTMLthelement.

Authors MUST ensure elements with rolerowheader are contained in, or owned by, an element with the role row.

scrollbar(role)

A graphical object that controls the scrolling of content within a viewing area, regardless of whether the content is fully displayed within the viewing area.

A scrollbar represents the current value and range of possible values via the size of the scrollbar and position of the thumb with respect to the visible range of the orientation (horizontal or vertical) it controls. Its orientation represents the orientation of the scrollbar and the scrolling effect on the viewing area controlled by the scrollbar. It is typically possible to add or subtract to the current value by using directional keys such as arrow keys.

Authors MUST set the aria-controls attribute on the scrollbar element to reference the scrollable area it controls.

Note: Elements with the role scrollbar have an implicit aria-orientation value of vertical.

Note: Assistive technologies generally will render the value of aria-valuenow as a percent of the range between the value of aria-valuemin and aria-valuemax, unless aria-valuetext is specified. It is best to set the values for aria-valuemin, aria-valuemax, and aria-valuenow in a manner that is appropriate for this calculation.

slider(role)

A user input where the user selects a value from within a given range.

A slider represents the current value and range of possible values via the size of the slider and position of the thumb. It is typically possible to add or subtract to the value by using directional keys such as arrow keys.

spinbutton(role)

A form of range that expects the user to select from among discrete choices.

A spinbutton typically allows the user to select from the given range through the use of an up and down button on the keyboard. Visibly, the current value is incremented or decremented until a maximum or minimum value is reached. Authors SHOULD ensure this functionality is accomplished programmatically through the use of up and down arrows on the keyboard.

Although a spinbutton is similar in appearance to many presentations of select, it is advisable to use spinbutton when working with known ranges (especially in the case of large ranges) as opposed to distinct options. For example, a spinbutton representing a range from 1 to 1,000,000 would provide much better performance than a selectwidget representing the same values.

structure(abstract role)

Roles for document structure support the accessibility of dynamic web content by helping assistive technologies determine active content versus static document content. Structural roles by themselves do not all map to accessibility APIs, but are used to create widget roles or assist content adaptation for assistive technologies.

Note: structure is an abstract role used for the ontology. Authors are instructed not to use this role in content.

Authors SHOULD ensure the tabpanel associated with the currently active tab is perceivable to the user.

For a single-selectable tablist, authors SHOULD hide other tabpanelelements from the user until the user selects the tab associated with that tabpanel. For a multi-selectable tablist, authors SHOULD ensure each visible tabpanel has its aria-expandedattribute set to true, and that the remaining hidden tabpanel elements have their aria-expanded attributes set to false.

In either case, authors SHOULD ensure that a selected tab has its aria-selected attribute set to true, that inactive tab elements have their aria-selected attribute set to false, and that the currently selected tab provides a visual indication that it is selected. In the absence of an aria-selected attribute on the current tab, user agentsSHOULD indicate to assistive technologies through the platform accessibility API that the currently focused tab is selected.

tablist(role)

For a single-selectable tablist, authors SHOULD hide other tabpanelelements from the user until the user selects the tab associated with that tabpanel. For a multi-selectable tablist, authors SHOULD ensure each visible tabpanel has its aria-expandedattribute set to true, and that the remaining hidden tabpanel elements have their aria-expanded attributes set to false.

textbox(role)

If the aria-multilineattribute is true, the widget accepts line breaks within the input, as in an HTML textarea. Otherwise, this is a simple text box. The intended use is for languages that do not have a text input element, or cases in which an element with different semantics is repurposed as a text field.

Note: In most user agent implementations, the default behavior of the ENTER or RETURN key is different between the single-line and multi-line text fields in HTML. When user has focus in a single-line <input type="text"> element, the keystroke usually submits the form. When user has focus in a multi-line <textarea> element, the keystroke inserts a line break. The WAI-ARIAtextbox role differentiates these types of boxes with the aria-multiline attribute, so authors are advised to be aware of this distinction when designing the field.

timer(role)

A type of live region containing a numerical counter which indicates an amount of elapsed time from a start point, or the time remaining until an end point.

The text contents of the timer object indicate the current time measurement, and are updated as that amount changes. The timer value is not necessarily machine parsable, but authors SHOULD update the text contents at fixed intervals, except when the timer is paused or reaches an end-point.

Note: Elements with the role timer maintain the default aria-live value of off.

toolbar(role)

A collection of commonly used function buttons or controls represented in compact visual form.

The toolbar is often a subset of functions found in a menubar, designed to reduce user effort in using these functions. Authors MUST supply an aria-label property on each toolbar when the application contains more than one toolbar.

Authors MAY manage focus of descendants for all instances of this role, as described in Managing Focus.

tooltip(role)

The tooltip typically becomes visible in response to a mouse hover, or after the owning element receives keyboard focus. In each of these cases, authors SHOULD display the tooltip after a short delay. The use of a WAI-ARIA tooltip is a supplement to the normal tooltip behavior of the user agent.

Note: Typical tooltip delays last from one to five seconds.

Authors SHOULD ensure that elements with the roletooltip are referenced through the use of aria-describedby by the time the tooltip is displayed.

treegrid(role)

A grid whose rows can be expanded and collapsed in the same manner as for a tree.

A treegrid is considered editable unless otherwise specified. To make a treegrid read-only, set the aria-readonly attribute of the treegrid to true. The value of the treegrid element's aria-readonly attribute is implicitly propagated to all of its owned gridcell elements, and will be exposed through the accessibility API. An author may override an individual gridcell element's propagated aria-readonly value by setting the aria-readonly attribute on the gridcell.

widget(abstract role)

Widgets are discrete user interface objects with which the user can interact. Widget roles map to standard features in accessibility APIs. When the user navigates an element assigned any of the non-abstract subclass roles of widget, assistive technologies that typically intercept standard keyboard events SHOULD switch to an application browsing mode, and pass keyboard events through to the web application. The intent is to hint to certain assistive technologies to switch from normal browsing mode into a mode more appropriate for interacting with a web application; some user agents have a browse navigation mode where keys, such as up and down arrows, are used to browse the document, and this native behavior prevents the use of these keys by a web application.

Note: widget is an abstract role used for the ontology. Authors are instructed not to use this role in content.

window(abstract role)

Elements with this role have a window-like behavior in a graphical user interface (GUI) context, regardless of whether they are implemented as a native window in the operating system, or merely as a section of the document styled to look like a window.

Note: window is an abstract role used for the ontology. Authors are instructed not to use this role in content.

6. Supported States and Properties

6.1. Clarification of States versus Properties

The terms "states" and "properties" refer to similar features. Both provide specific information about an object, and both form part of the definition of the nature of roles. In this document, states and properties are both treated as aria-prefixed markup attributes. However, they are maintained conceptually distinct to clarify subtle differences in their meaning. One major difference is that the values of properties (such as aria-labelledby) are often less likely to change throughout the application life-cycle than the values of states (such as aria-checked) which may change frequently due to user interaction. Note that the frequency of change difference is not a rule; a few properties, such as aria-activedescendant, aria-valuenow, and aria-valuetext are expected to change often. Because the distinction between states and properties is of little consequence to most web content authors, this specification refers to both "states" and "properties" simply as "attributes" whenever possible. See the definitions of state and property for more information.

6.2. Characteristics of States and Properties

6.2.1. Related Concepts

Advisory information about features from this or other languages that correspond to this state or property. While the correspondence may not be exact, it is useful to help understand the intent of the state or property.

6.2.2. Used in Roles

Advisory information about roles that use this state or property. This information is provided to help understand the appropriate usage of the state or property. Use of a given state or property is not defined when used on roles other than those listed.

The "undefined" value, when allowed on a state or property, is an explicit indication that the state or property is not set. The value is used on states and properties that support tokens, and the "undefined" value is a string that is one of the allowed tokens. It is also used on some states and properties that accept true/false values, when "undefined" has a different meaning than "false".

These are generic types for states and properties, but do not define specific representation. See State and Property Attribute Processing for details on how these values are expressed and handled in host languages.

6.3. Values for States and Properties

Many states and properties accept a specific set of tokens as values. The allowed values and explanation of their meaning is shown after the table of characteristics. The default value, if defined, is shown in strong type, followed by the parenthetical term 'default'. When a value is indicated as the default, the user agent MUST follow the behavior prescribed by this value when the state or property is empty or undefined. Some roles also define what behavior to use when certain states or properties, that do not have default values, are not provided.

6.4. Global States and Properties

Some states and properties are applicable to all host language elements regardless of whether a role is applied. The following global states and properties are supported by all roles and by all base markup elements.

Global states and properties are applied to the role roletype, which is the base role, and therefore inherit into all roles. To facilitate reading, they are not explicitly identified as either supported or inherited states and properties in the specification. Instead, the inheritance is indicated by a link to this section.

6.5. Taxonomy of WAI-ARIA States and Properties

6.5.1. Widget Attributes

This section contains attributes specific to common user interface elements found on GUI systems or in rich internet applications which receive user input and process user actions. These attributes are used to support the widget roles.

Widget attributes might be mapped by a user agent to platform accessibility APIstates, for access by assistive technologies, or they might be accessed directly from the DOM. User agents MUST provide a way for assistive technologies to be notified when states change, either through DOM attribute change events or platform accessibility API events.

6.5.2. Live Region Attributes

This section contains attributes specific to live regions in rich internet applications. These attributes may be applied to any element. The purpose of these attributes is to indicate that content changes may occur without the element having focus, and to provide assistive technologies with information on how to process those content updates. Some roles specify a default value for the aria-live attribute specific to that role. An example of a live region is a ticker section that lists updating stock quotes.

6.5.3. Drag-and-Drop Attributes

This section lists attributes which indicate information about drag-and-drop interface elements, such as draggable elements and their drop targets. Drop target information will be rendered visually by the author and provided to assistive technologies through an alternate modality.

Indicates what functions can be performed when the dragged object is released on the drop target. This allows assistive technologies to convey the possible drag options available to users, including whether a pop-up menu of choices is provided by the application. Typically, drop effect functions can only be provided once an object has been grabbed for a drag operation as the drop effect functions available are dependent on the object being dragged.

Identifies the next element (or elements) in an alternate reading order of content which, at the user's discretion, allows assistive technology to override the general default of reading in document source order.

Identifies an element (or elements) in order to define a visual, functional, or contextual parent/child relationship between DOM elements where the DOM hierarchy cannot be used to represent the relationship. See related aria-controls.

aria-activedescendant(property)

This is used when a composite widget is responsible for managing its current active child to reduce the overhead of having all children be focusable. Examples include: multi-level lists, trees, and grids. In some implementations the user agent may use aria-activedescendant to tell assistive technologies that the active descendant has focus. Authors MAY use the aria-activedescendant attribute on the focused descendant of a composite widget; for example, on a textbox descendant of a combo box.

Authors SHOULD ensure that the element targeted by the aria-activedescendantattribute is either a descendant of the container in the DOM, or is a logical descendant as indicated by the aria-owns attribute. The user agent is not expected to validate that the active descendant is a descendant of the container. Authors SHOULD ensure that the currently active descendant is visible and in view (or scrolls into view) when focused.

When the content of a live region changes, user agents SHOULD examine the changed element and traverse the ancestors to find the first element with aria-atomic set, and apply the appropriate behavior for the cases below.

If none of the ancestors have explicitly set aria-atomic, the default is that aria-atomic is false, and assistive technologies will only present the changed node to the user.

If aria-atomic is explicitly set to false, assistive technologies will stop searching up the ancestor chain and present only the changed node to the user.

If aria-atomic is explicitly set to true, assistive technologies will present the entire contents of the element.

When aria-atomic is true, assistive technologies MAY choose to combine several changes and present the entire changed region at once.

aria-busy(state)

Indicates whether an element, and its subtree, are currently being updated.

The default is that aria-busy is false. If authors know that multiple parts of the same element need to be loaded or modified, they can set aria-busy to true when the first part is loaded, and then set aria-busy to false when the last part is loaded. When a widget is missing required owned elements due to script execution or loading, authors MUST mark a containing element with aria-busy equal to true. For example, until a page is fully initialized and complete, an author could mark the document element as busy. If there is an error updating the element, author MAY set the aria-invalid attribute to true.

aria-checked(state)

The aria-checkedattribute indicates whether the element is checked (true), unchecked (false), or represents a group of other elements that have a mixture of checked and unchecked values (mixed). Most inputs only support values of true and false, but the mixed value is supported by certain tri-state inputs such as a checkbox or menuitemcheckbox.

aria-describedby(property)

The aria-labelledby attribute is similar to aria-describedby in that both reference other elements to calculate a text alternative, but a label should be concise, where a description is intended to provide more verbose information.

The element or elements referenced by the aria-describedby comprise the entire description. Include ID references to multiple elements if necessary, or enclose a set of elements (e.g., paragraphs) with the element referenced by the ID.

aria-disabled(state)

For example, irrelevant options in a radio group may be disabled. Disabled elements might not receive focus from the tab order. For some disabled elements, applications might choose not to support navigation to descendants. In addition to setting the aria-disabled attribute, authors SHOULD change the appearance (grayed out, etc.) to indicate that the item has been disabled.

The state of being disabled applies to the current element and all focusable descendant elements of the element on which the aria-disabledattribute is applied.

aria-dropeffect(property)

Indicates what functions can be performed when the dragged object is released on the drop target. This allows assistive technologies to convey the possible drag options available to users, including whether a pop-up menu of choices is provided by the application. Typically, drop effect functions can only be provided once an object has been grabbed for a drag operation as the drop effect functions available are dependent on the object being dragged.

More than one drop effect may be supported for a given element. Therefore, the value of this attribute is a space-delimited set of tokens indicating the possible effects, or none if there is no supported operation. In addition to setting the aria-dropeffect attribute, authors SHOULD show a visual indication of potential drop targets.

The source object will be removed from its current location and dropped into the target.

link:

A reference or shortcut to the dragged object will be created in the target object.

execute:

A function supported by the drop target is executed, using the drag source as an input.

popup:

There is a popup menu or dialog that allows the user to choose one of the drag operations (copy, move, link, execute) and any other drag functionality, such as cancel.

none (default):

No operation can be performed; effectively cancels the drag operation if an attempt is made to drop on this object. Ignored if combined with any other token value. e.g. 'none copy' is equivalent to a 'copy' value.

aria-expanded(state)

Indicates whether the element, or another grouping element it controls, is currently expanded or collapsed.

For example, this indicates whether a portion of a tree is expanded or collapsed. In other instances, this may be applied to page sections to mark expandable and collapsible regions that are flexible for managing content density. Simplifying the user interface by collapsing sections may improve usability for all, including those with cognitive or developmental disabilities.

If the element with the aria-expanded attribute controls the expansion of another grouping container that is not 'owned by' the element, the author SHOULD reference the container by using the aria-controls attribute.

aria-flowto(property)

Identifies the next element (or elements) in an alternate reading order of content which, at the user's discretion, allows assistive technology to override the general default of reading in document source order.

When aria-flowto has a single IDREF, it allows assistive technologies to, at the user's request, forego normal document reading order and go to the targeted object. However, when aria-flowto is provided with multiple IDREFS, assistive technologies SHOULD present the referenced elements as path choices.

In the case of one or more IDREFS, user agents or assistive technologies SHOULD give the user the option of navigating to any of the targeted elements. The name of the path can be determined by the name of the target element of the aria-flowtoattribute. Accessibility APIs can provide named path relationships.

aria-grabbed(state)

When it is set to true it has been selected for dragging, false indicates that the element can be grabbed for a drag-and-drop operation, but is not currently grabbed, and undefined (or no value) indicates the element cannot be grabbed (default).

When aria-grabbed is set to true, authors SHOULD update the aria-dropeffectattribute of all potential drop targets. When an element is not grabbed (the value is set to false, undefined, or the attribute is removed), authors SHOULD revert the aria-dropeffect attributes of the associated drop targets to none.

aria-hidden(state)

If an element is only visible after some user action, authors MUST set the aria-hiddenattribute to true. When the element is presented, authors MUST set the aria-hidden attribute to false or remove the attribute, indicating that the element is visible. Some assistive technologies access WAI-ARIA information directly through the DOM and not through platform accessibility supported by the browser. Authors MUST set aria-hidden="true" on content that is not displayed, regardless of the mechanism used to hide it. This allows assistive technologies or user agents to properly skip hidden elements in the document.

It is recommended that authors key visibility of elements off this attribute, rather than change visibility and separately have to remember to update this property. CSS 2 provides a way to select on attribute values ([CSS]). The following CSS declaration makes content visible unless the aria-hidden attribute is true; scripts need only update the value of this attribute to change visibility:

[aria-hidden="true"] { visibility: hidden; }

Note: Authors are reminded that visibility:hidden and display:none apply to allCSS media types; therefore, use of either will hide the content from assistive technologies that access the DOM through a rendering engine. However, in order to support assistive technologies that access the DOM directly, or other authoring techniques to visibly hide content (for example, opacity or off-screen positioning), authors need to ensure the aria-hidden attribute is always updated accordingly when an element is shown or hidden, unless the intent of using off-screen positioning is to make the content visible only to screen reader users and not others.

Authors MAY, with caution, use aria-hidden to hide visibly rendered content from assistive technologies only if the act of hiding this content is intended to improve the experience for users of assistive technologies by removing redundant or extraneous content. Authors using aria-hidden to hide visible content from screen readers MUST ensure that identical or equivalent meaning and functionality is exposed to assistive technologies.

Note: Authors are advised to use extreme caution and consider a wide range of disabilities when hiding visibly rendered content from assistive technologies. For example, a sighted, dexterity-impaired individual may use voice-controlled assistive technologies to access a visual interface. If an author hides visible link text "Go to checkout" and exposes similar, yet non-identical link text "Check out now" to the accessibility API, the user may be unable to access the interface they perceive using voice control. Similar problems may also arise for screen reader users. For example, a sighted telephone support technician may attempt to have the blind screen reader user click the "Go to checkout" link, which they may be unable to find using a type-ahead item search ("Go to…").

Indicates that this section of the document and its children are hidden from the rendered view.

false (default):

Indicates that this section of the document is rendered.

Note: Authors are advised to avoid using aria-hidden="false" with styles or attributes that have historically prevented rendering in all modalities, such as display:none or visibility:hidden in CSS, or the hidden attribute in HTML 5. At the time of this writing, aria-hidden="false" is known to work inconsistently when used in conjunction with such features. As future implementations improve, use caution and test thoroughly before relying on this approach.

aria-invalid(state)

Indicates the entered value does not conform to the format expected by the application.

If the value is computed to be invalid or out-of-range, the application author SHOULD set this attribute to true. User agentsSHOULD inform the user of the error. Application authors SHOULD provide suggestions for corrections if they are known. Authors MAY prevent form submission when an associated form element has its aria-invalid attribute set to true.

When the user attempts to submit data involving a field for which aria-required is true, authors MAY use the aria-invalid attribute to signal there is an error. However, if the user has not attempted to submit the form, authors SHOULD NOT set the aria-invalid attribute on required widgets simply because the user has not yet entered data.

For future expansion, the aria-invalid attribute is an enumerated type. Any value not recognized in the list of allowed valuesMUST be treated by user agents as if the value true had been provided. If the attribute is not present, or its value is false, or its value is an empty string, the default value of false applies.

Characteristics of aria-invalid

Characteristic

Value

Related Concepts:

XForms [XForms] 'invalid' event http://www.w3.org/TR/2006/REC-xforms-20060314/slice4.html#evt-revalidate. Note: This state is true if a form field is required but empty. However, the XForms valid property would be set to false.

If the label text is visible on screen, authors SHOULD use aria-labelledby and SHOULD NOT use aria-label. There may be instances where the name of an element cannot be determined programmatically from the content of the element, and there are cases where providing a visible label is not the desired user experience. Most host languages provide an attribute that could be used to name the element (e.g., the title attribute in HTML [HTML]), yet this could present a browser tooltip. In the cases where a visible label or visible tooltip is undesirable, authors MAY set the accessible name of the element using aria-label. As required by the text alternative computation, user agents give precedence to aria-labelledby over aria-label when computing the accessible name property.

aria-labelledby(property)

The purpose of aria-labelledby is the same as that of aria-label. It provides the user with a recognizable name of the object. The most common accessibility API mapping for a label is the accessible name property.

If the label text is visible on screen, authors SHOULD use aria-labelledby and SHOULD NOT use aria-label. Use aria-label only if the interface is such that it is not possible to have a visible label on the screen. As required by the text alternative computation, user agents give precedence to aria-labelledby over aria-label when computing the accessible name property.

The aria-labelledby attribute is similar to aria-describedby in that both reference other elements to calculate a text alternative, but a label should be concise, where a description is intended to provide more verbose information.

Note: The expected spelling of this property in U.S. English is "labeledby." However, the accessibility API features to which this property is mapped have established the "labelledby" spelling. This property is spelled that way to match the convention and minimize the difficulty for developers.

aria-level(property)

This can be applied inside trees to tree items, to headings inside a document, to nested grids, nested tablists and to other structural items that may appear inside a container or participate in an ownership hierarchy. The value for aria-level is an integer greater than or equal to 1.

Levels increase with depth. If the DOM ancestry does not accurately represent the level, authors SHOULD explicitly define the aria-levelattribute.

This attribute is applied to elements that act as leaf nodes within the orientation of the set, for example, on elements with role treeitem rather than elements with role group. This means that multiple elements in a set may have the same value for this attribute. Although it would be less repetitive to provide a single value on the container, restricting this to leaf nodes ensures that there is a single way for assistive technologies to use the attribute.

If the DOM ancestry accurately represents the level, the user agent can calculate the level of an item from the document structure. This attribute can be used to provide an explicit indication of the level when that is not possible to calculate from the document structure or the aria-owns attribute. User agent support for automatic calculation of level may vary; authors SHOULD test with user agents and assistive technologies to determine whether this attribute is needed. If the author intends for the user agent to calculate the level, the author SHOULD omit this attribute.

Note: In the case of a treegrid, aria-level is supported on elements with the role row, not elements with role gridcell. At first glance, this may seem inconsistent with the application of aria-level on treeitem elements, but it is consistent in that the row acts as the leaf node within the vertical orientation of the grid, whereas the gridcell is a leaf node within the horizontal orientation of each row. Level is not supported on sets of cells within rows, so the aria-level attribute is applied to the element with the role row.

aria-live(property)

The values of this attribute are expressed in degrees of importance. When regions are specified as polite, assistive technologies will notify users of updates but generally do not interrupt the current task, and updates take low priority. When regions are specified as assertive, assistive technologies will immediately notify the user, and could potentially clear the speech queue of previous updates. Please refer to Live Region Properties and How to Use Them ([ARIA-PRACTICES], Section 5.2.1).

Politeness levels are essentially an ordering mechanism for updates and serve as a strong suggestion to user agents or assistive technologies. The value may be overridden by user agents, assistive technologies, or the user. For example, if assistive technologies can determine that a change occurred in response to a key press or a mouse click, the assistive technologies may present that change immediately even if the value of the aria-live attribute states otherwise.

Since different users have different needs, it is up to the user to tweak his or her assistive technologies' response to a live region with a certain politeness level from the commonly defined baseline. Assistive technologies may choose to implement increasing and decreasing levels of granularity so that the user can exercise control over queues and interruptions.

When the property is not set on an object that needs to send updates, the politeness level is the value of the nearest ancestor that sets the aria-live attribute.

The aria-live attribute is the primary determination for the order of presentation of changes to live regions. Implementations will also consider the default level of politeness in a role when the aria-live attribute is not set in the ancestor chain (e.g., log changes are polite by default). Items which are assertive will be presented immediately, followed by polite items. User agents or assistive technologies MAY choose to clear queued changes when an assertive change occurs. (e.g., changes in an assertive region may remove all currently queued changes)

Updates to the region will not be presented to the user unless the assitive technology is currently focused on that region.

polite:

(Background change) Assistive technologies SHOULD announce updates at the next graceful opportunity, such as at the end of speaking the current sentence or when the user pauses typing.

assertive:

This information has the highest priority and assistive technologies SHOULD notify the user immediately. Because an interruption may disorient users or cause them to not complete their current task, authors SHOULD NOT use the assertive value unless the interruption is imperative.

aria-multiline(property)

Indicates whether a text box accepts multiple lines of input or only a single line.

Note: In most user agent implementations, the default behavior of the ENTER or RETURN key is different between the single-line and multi-line text fields in HTML. When user has focus in a single-line <input type="text"> element, the keystroke usually submits the form. When user has focus in a multi-line <textarea> element, the keystroke inserts a line break. The WAI-ARIAtextbox role differentiates these types of boxes with the aria-multiline attribute, so authors are advised to be aware of this distinction when designing the field.

aria-multiselectable(property)

Indicates that the user may select more than one item from the current selectable descendants.

Authors SHOULD ensure that selected descendants have the aria-selectedattribute set to true, and selectable descendant have the aria-selected attribute set to false. Authors SHOULD NOT use the aria-selected attribute on descendants that are not selectable.

Note: Lists and trees are examples of roles that might allow users to select more than one item at a time.

aria-owns(property)

Identifies an element (or elements) in order to define a visual, functional, or contextual parent/child relationship between DOM elements where the DOM hierarchy cannot be used to represent the relationship. See related aria-controls.

The value of the aria-ownsattribute is a space-separated list of IDREFS that reference one or more elements in the document by ID. The reason for adding aria-owns is to expose a parent/child contextual relationship to assistive technologies that is otherwise impossible to infer from the DOM.

Authors SHOULD NOT use aria-owns as a replacement for the DOM hierarchy. If the relationship is represented in the DOM, do not use aria-owns. Authors MUST ensure that an element's ID is not specified in more than one other element's aria-owns attribute at any time. In other words, an element can have only one explicit owner.

aria-posinset(property)

Defines an element's number or position in the current set of listitems or treeitems. Not required if all elements in the set are present in the DOM. See related aria-setsize.

If all items in a set are present in the document structure, it is not necessary to set this attribute, as the user agent can automatically calculate the set size and position for each item. However, if only a portion of the set is present in the document structure at a given moment, this property is needed to provide an explicit indication of an element's position.

aria-pressed(state)

Toggle buttons require a full press-and-release cycle to change their value. Activating it once changes the value to true, and activating it another time changes the value back to false. A value of mixed means that the values of more than one item controlled by the button do not all share the same value. Examples of mixed-state buttons are described in WAI-ARIA Authoring Practices [ARIA-PRACTICES]. If the attribute is not present, the button is not a toggle button.

The aria-pressed attribute is similar but not identical to the aria-checked attribute. Operating systems support pressed on buttons and checked on checkboxes.

aria-readonly(property)

This means the user can read but not set the value of the widget. Readonly elements are relevant to the user, and application authors SHOULD NOT restrict navigation to the element or its focusable descendants. Other actions such as copying the value of the element are also supported. This is in contrast to disabled elements, to which applications might not allow user navigation to descendants.

aria-relevant(property)

Indicates what user agent change notifications (additions, removals, etc.) assistive technologies will receive within a live region. See related aria-atomic.

The attribute is represented as a space delimited list of the following values: additions, removals, text; or a single catch-all value all.

This is used to describe semantically meaningful changes, as opposed to merely presentational ones. For example, nodes that are removed from the top of a log are merely removed for purposes of creating room for other entries, and the removal of them does not have meaning. However, in the case of a buddy list, removal of a buddy name indicates that they are no longer online, and this is a meaningful event. In that case aria-relevant will be set to all. When the aria-relevant attribute is not provided, the default value, additions text, indicates that text modifications and node additions are relevant, but that node removals are irrelevant.

Note: aria-relevant values of removals or all are to be used sparingly. Assistive technologies only need to be informed of content removal when its removal represents an important change, such as a buddy leaving a chat room.

Note: Text removals should only be considered relevant if one of the specified values is 'removals' or 'all'. For example, for a text change from 'foo' to 'bar' in a live region with a default aria-relevant value, the text addition ('bar') would be spoken, but the text removal ('foo') would not.

aria-relevant is an optional attribute of live regions. This is a suggestion to assistive technologies, but assistive technologies are not required to present changes of all the relevant types.

When aria-relevant is not defined, an element's value is inherited from the nearest ancestor with a defined value. Although the value is a token list, inherited values are not additive; the value provided on a descendant element completely overrides any inherited value from an ancestor element.

When text changes are denoted as relevant, user agents MUST monitor any descendant node change that affects the text alternative computation of the live region as if the accessible name were determined from contents (nameFrom: contents). For example, a text change would be triggered if the HTML alt attribute of a contained image changed. However, no change would be triggered if there was a text change to a node outside the live region, even if that node was referenced (via aria-labelledby) by an element contained in the live region.

aria-required(property)

Indicates that user input is required on the element before a form may be submitted.

For example, if the user needs to fill in an address field, the author will need to set the field's aria-required attribute to true.

Note: The fact that the element is required is often presented visually (such as a sign or symbol after the widget). Using the aria-requiredattribute allows the author to explicitly convey to assistive technologies that an element is required.

Unless an exactly equivalent native attribute is available, host languages SHOULD allow authors to use the aria-required attribute on host language form elements that require input or selection by the user.

aria-selected(state)

This attribute is used with single-selection and multiple-selection widgets:

Single-selection containers where the currently focused item is not selected. The selection normally follows the focus, and is managed by the user agent.

Multiple-selection containers. Authors SHOULD ensure that any selectable descendant of a container in which the aria-multiselectable attribute is true specifies a value of either true or false for the aria-selected attribute.

Any explicit assignment of aria-selected takes precedence over the implicit selection based on focus. If no DOM element in the widget is explicitly marked as selected, assistive technologies MAY convey implicit selection which follows the keyboard focus of the managed focus widget. If any DOM element in the widget is explicitly marked as selected, the user agent MUST NOT convey implicit selection for the widget.

aria-setsize(property)

Defines the number of items in the current set of listitems or treeitems. Not required if all elements in the set are present in the DOM. See related aria-posinset.

This property is marked on the members of a set, not the container element that collects the members of the set. To orient the user by saying an element is "item X out of Y," the assistive technologies would use X equal to the aria-posinsetattribute and Y equal to the aria-setsize attribute.

If all items in a set are present in the document structure, it is not necessary to set this property, as the user agent can automatically calculate the set size and position for each item. However, if only a portion of the set is present in the document structure at a given moment (in order to reduce document size), this property is needed to provide an explicit indication of set size.

aria-sort(property)

Indicates if items in a table or grid are sorted in ascending or descending order.

Authors SHOULD only apply this property to table headers or grid headers. If the property is not provided, there is no defined sort order. For each table or grid, authors SHOULD apply aria-sort to only one header at a time.

aria-valuemax(property)

A range widget may start with a given value, which can be increased until a maximum value, defined by this property, is reached.

Declaring the minimum and maximum values allows alternate devices to react to arrow keys, validate the current value, or simply let the user know the size of the range. If the aria-valuenow has a known maximum and minimum, the author SHOULD provide properties for aria-valuemax and aria-valuemin. Authors MUST ensure the value of aria-valuemax is greater than or equal to the value of aria-valuemin.

aria-valuemin(property)

A range widget may start with a given value, which can be decreased until a minimum value, defined by this property, is reached.

Declaring the minimum and maximum values allows alternate devices to react to arrow keys, validate the current value, or simply let the user know the size of the range. If the aria-valuenow has a known maximum and minimum, the author SHOULD provide properties for aria-valuemax and aria-valuemin.

Authors MUST ensure the value of aria-valuemin is less than or equal to the value of aria-valuemax.

aria-valuenow(property)

This property is used, for example, on a range widget such as a slider or progress bar.

If the current value is not known (for example, an indeterminate progress bar), the author SHOULD NOT set the aria-valuenowattribute. If the aria-valuenow attribute is absent, no information is implied about the current value. If the aria-valuenow has a known maximum and minimum, the author SHOULD provide properties for aria-valuemax and aria-valuemin.

The value of aria-valuenow is a decimal number. If the range is a set of numeric values, then aria-valuenow is one of those values. For example, if the range is [0, 1], a valid aria-valuenow is 0.5. A value outside the range, such as -2.5 or 1.1, is invalid.

For progressbar elements and scrollbar elements, assistive technologies SHOULD render the value to users as a percent, calculated as a position on the range from aria-valuemin to aria-valuemax if both are defined, otherwise the actual value with a percent indicator. For elements with role slider and spinbutton, assistive technologies SHOULD render the actual value to users.

When the rendered value cannot be accurately represented as a number, authors SHOULD use the aria-valuetext attribute in conjunction with aria-valuenow to provide a user-friendly representation of the range's current value. For example, a slider may have rendered values of small, medium, and large. In this case, the values of aria-valuenow could range from 1 through 3, which indicate the position of each value in the value space, but the aria-valuetext would be one of the strings: small, medium, or large.

Note: If aria-valuetext is specified, assistive technologies render that instead of the value of aria-valuenow.

aria-valuetext(property)

This property is used, for example, on a range widget such as a slider or progress bar.

If the aria-valuetextattribute is set, authors SHOULD also set the aria-valuenow attribute, unless that value is unknown (for example, on an indeterminate progressbar).

Authors SHOULD only set the aria-valuetext attribute when the rendered value cannot be meaningfully represented as a number. For example, a slider may have rendered values of small, medium, and large. In this case, the values of aria-valuenow could range from 1 through 3, which indicate the position of each value in the value space, but the aria-valuetext would be one of the strings: small, medium, or large. If the aria-valuetext attribute is absent, the assistive technologies will rely solely on the aria-valuenow attribute for the current value.

If aria-valuetext is specified, assistive technologies SHOULD render that value instead of the value of aria-valuenow.

7. Implementation in Host Languages

The roles, states, and properties defined in this specification do not form a complete web language or format. They are intended to be used in the context of a host language. This section discusses how host languages are to implement WAI-ARIA, to ensure that the markup specified here will integrate smoothly and effectively with the host language markup.

Although markup languages look alike superficially, they do not share language definition infrastructure. To accommodate differences in language-building approaches, the requirements are both general and modularization-specific. While allowing for differences in how the specifications are written, the intent is to maintain consistency in how the WAI-ARIA information looks to authors and how it is manipulated in the DOM by scripts.

WAI-ARIA roles, states, and properties are implemented as attributes of elements. Roles are applied by placing their names among the tokens appearing in the value of a host-language-provided role attribute. States and properties each get their own attribute, with values as defined for each particular state or property in this specification. The name of the attribute is the aria-prefixed name of the state or property.

7.2. State and Property Attributes

An implementing host language MUST allow attributes with the following characteristics:

The attribute name is the name of any state or property identified in the Supported States and Properties section, such as aria-busy, aria-selected, aria-activedescendant, aria-valuetext;

The syntax does NOT prevent the attribute from appearing anywhere that it is applicable, as specified in this specification;

When these attributes appear in a document instance, the attributes will be processed as defined in this specification.

Host languages that support XML Namespaces [XML-NAMES] MAY require that WAI-ARIA attributes be used with a namespace. In this case, the namespace for WAI-ARIA state and property attributes MUST be http://www.w3.org/ns/wai-aria/. To use WAI-ARIA in host languages that do not explicitly describe support for it, authors SHOULD use this namespace as well, if the host language supports namespaces and there is expectation that user agents will recognize the WAI-ARIA namespace. The namespace prefix is not defined by this specification but generally is expected to be "aria".

Note: The WAI-ARIA state and property attributes have a naming convention such that they all begin with the string "aria-". This is not a namespace prefix, it is a part of the state or property name. Therefore, when using WAI-ARIA states and properties with namespace prefixes, the complete attribute name will be like "aria:aria-foo".

Some host languages do not use namespaces with WAI-ARIA state and property attributes, either because the host language does not support namespaces or because the designers wish to incorporate WAI-ARIA into the core feature set. In these host languages, the namespace name for these attributes has no value. The names of these attributes do not have a prefix offset by a colon; in the terms of namespaces they are unprefixed attribute names. The ECMAScript binding of the DOM interface getAttributeNS for example, treats an empty string ("") as representing this condition, so that both getAttribute("aria-busy") and getAttributeNS("", "aria-busy") access the same aria-busy attribute in the DOM.

Note: According to the requirements of this section, some user agents recognize WAI-ARIA state and property attributes with namespaces, some without namespaces, and some might recognize both. Authors are advised to be aware of which form is supported for the host language they are using. Unless the host language and supporting user agents explicitly indicate that the namespace is required, authors are advised to use the attribute without namespaces. Even user agents that support namespaces generally do not publish namespaced WAI-ARIA states and properties to accessibility APIs. In particular, current implementations of HTML, including XHTML, do not support this namespace.

7.3. Focus Navigation

An implementing host language MUST provide support for the author to make all interactive elements focusable, that is, any renderable or event-receiving elements. An implementing host language MUST provide a facility to allow web authors to define whether these focusable, interactive elements appear in the default tab navigation order. The tabindexattribute in HTML 5 is an example of one implementation.

7.4. Implicit WAI-ARIA Semantics

WAI-ARIA is designed to provide semantic information about objects when host languages lack native semantics for the object. WAI-ARIA is designed, however, to provide additional semantics for many host languages. Furthermore, host languages over time can evolve and provide new native features that correspond to WAI-ARIA features. Therefore, there are many situations in which WAI-ARIA semantics are redundant with host language semantics.

These host language features can be viewed as having "implicit WAI-ARIA semantics". User agent processing of features with implicit WAI-ARIA semantics would be similar to the processing for the WAI-ARIA feature. The processing might not be identical because of lexical differences between the host language feature and the WAI-ARIA feature, but generally the user agent would expose the same information to the accessibility API. Features with implicit WAI-ARIA semantics satisfy WAI-ARIA structural requirements such as required owned elements, required states and properties, etc. and do not require explicit WAI-ARIA semantics to be provided.

For example, if an element with the functionality already exists, such as a checkbox or radio button, use the native semantics of the host language. WAI-ARIA markup is only intended to be used to enhance the native semantics (e.g., indicating that the element is required with aria-required), or to change the semantics to a different purpose form the standard functionality of the element.

Implicit WAI-ARIA semantics affect the conflict resolution procedures in the following section, Conflicts with Host Language Semantics. Therefore, implicit WAI-ARIA semantics need to be defined in a normative specification, such as the host language specification or the WAI-ARIA User Agent Implementation Guide [ARIA-IMPLEMENTATION].

7.5. Conflicts with Host Language Semantics

WAI-ARIA roles, states, and properties are intended to add semantic information when native host language elements with these semantics are not available, and are generally used on elements that have no native semantics of their own. They can also be used on elements that have similar but non-identical semantics (for example, a nested list could be used to represent a tree structure). This method can be part of a fallback strategy for older browsers that have no WAI-ARIA implementation, or because native presentation of the repurposed element reduces the amount of style and/or script needed. Except for the cases outlined below, user agents MUST always use the WAI-ARIA semantics to define how it exposes the element to accessibility APIs, rather than using the host language semantics.

In addition to these normal situations in which WAI-ARIA is expected to override native semantics, there are elements that are inappropriate to override with WAI-ARIA. This could be because identical host language semantics exist, so WAI-ARIA is not needed, or because semantics from WAI-ARIA directly conflict with host language semantics. When a feature in the host language with identical role semantics and values is available, and the author has no compelling reason to avoid using the host language feature, authors SHOULD use the host language features rather than repurpose other elements with WAI-ARIA.

Host languages can have features that have implicit WAI-ARIA semantics corresponding to roles. When a WAI-ARIA role is provided, user agents MUST use the semantic of the WAI-ARIA role for processing, not the native semantic, unless the role requires WAI-ARIA states and properties whose attributes are explicitly forbidden on the native element by the host language. Values for roles do not conflict in the same way as values for states and properties (for example, the HTML 'checked' attribute and the 'aria-checked' attribute could have conflicting values), and authors are expected to have valid reason to provide a WAI-ARIA role even on elements that would not normally be repurposed.

When WAI-ARIA states and properties correspond to host language features that have the same implicit WAI-ARIA semantic, it can be particularly problematic to use the WAI-ARIA feature. If the WAI-ARIA feature and the host language feature are both provided but their values are not kept in sync, user agents and assistive technologies cannot know which value to use. Therefore, to prevent providing conflicting states and properties to assistive technologies, host languages MUST explicitly declare where the use of WAI-ARIA attributes on each host language element conflicts with native attributes for that element. When a host language declares a WAI-ARIA attribute to be in direct semantic conflict with a native attribute for a given element, user agents MUST ignore the WAI-ARIA attribute and instead use the host language attribute with the same implicit semantic.

Host languages MAY document features that cannot be overridden with WAI-ARIA (these are called "strong native semantics"). These can be features that have implicit WAI-ARIA semantics, as well as features where the processing would be uncertain if the semantics were changed with WAI-ARIA. Conformance checkers MAY signal an error or warning when a WAI-ARIA role is used on elements with strong native semantics, but as described above, user agents MUST still use the value of the the semantic of the WAI-ARIA role when exposing the element to accessibility APIs.

7.6. State and Property Attribute Processing

State and property attributes are included in host languages, and therefore syntax for representation of their value types is governed by the host language. For each of the value types defined in Value, an appropriate value type from the host language is used. Recommended correspondences between WAI-ARIA value types and various host language value types are listed in Mapping WAI-ARIA Value types to languages. This is a non-normative mapping in order to accommodate new host languages supporting WAI-ARIA.

The list value types—ID reference list and token list—allow more than one value of the given type to be provided. The values are separated by delimiter characters recognized by the host language for list attributes, such as space characters, commas, etc. Some languages may require a specific, single delimiter, while others may allow various delimiters.

Global states and properties are supported on any element in the host language. However, authors MUST only use non-global states and properties on elements with a role supporting the state or property; either defined as an explicit WAI-ARIA role, or as defined by the host language semantic matching an appropriate WAI-ARIA role. When a role attribute is added to an element, the semantics and behavior of the element, including support for WAI-ARIA states and properties, are augmented or overridden by the role behavior. User agents MUST ignore non-global states and properties used on an element without a role supporting the state or property; either defined as an explicit WAI-ARIA role, or as defined by the host language semantic matching an appropriate WAI-ARIA role. For example, the aria-valuetext attribute may be used on a progress element in HTML, without requiring the author to explicitly and redundantly specify the role as progressbar.

When WAI-ARIA roles are used, supported states and properties that are not present in the DOM are treated according to their default value, unless they are required. For token states and properties, an attribute value that is a zero-length string ("") also corresponds to the default value. Therefore, user agents SHOULD treat token state and property attributes with a value of "" the same as they treat an absent attribute. Normally this corresponds to the default value (usually "undefined"), but if it is a required attribute, they signal an error (because a null value is the same as failing to provide the required attribute).

8. Conformance

8.1. Non-interference with the Host Language

WAI-ARIA processing by the user agentMUST NOT interfere with the normal operation of the built-in features of the host language.

If a CSS selector includes a WAI-ARIA attribute (e.g., input[aria-invalid="true"]), user agents MUST update the visual display of any elements matching (or no longer matching) the selector any time the attribute is added/changed/removed in the DOM. The user agent MAY alter the mapping of the host language features into an accessibility API, but the user agent MUST NOT alter the DOM in order to remap WAI-ARIA markup into host language features.

8.2. All WAI-ARIA in DOM

A conforming user agent which implements a document object model that does not conform to the W3C DOM specification MUST include the content attribute for role and its WAI-ARIA role values, as well as the WAI-ARIA States and Properties in the DOM as specified by the author, even though processing may affect how the elements are exposed to accessibility APIs. Doing so ensures that each role attribute and all WAI-ARIA states and properties, including their values, are in the document in an unmodified form so other tools, such as assistive technologies, can access them. A conforming W3C DOM meets this criteria.

Assistive technologies, such as voice recognition systems and alternate input devices for users with mobility impairments, require the ability to control a web application in a device-independent way. WAI-ARIAstates and properties reflect the current state of rich internet application components. The ability for assistive technologies to notify web application of necessary changes is essential because it allows these alternative input solutions to control an application without being dependent on the standard input device which the user is unable to effectively control directly.

User agents MUST provide a method to notify the web application when a change occurs to states or properties in the system accessibility API. Likewise, web application authors SHOULD update the web application accordingly when notified of a change request from the user agent or assistive technology.

Note: Many state and properties can be changed by assistive technologies through existing accessibility APIs by responding to a default action event. For example, the aria-selected state of a tab in a tabpanel can be changed by triggering the default action on the element.

8.4. Conformance Checkers

Any application or script verifying document conformance or validity SHOULD include a test for all of the normative author requirements in this specification. If testing for a given requirement, conformance checkers MUST issue an error if an author "MUST" requirement isn't met, and MUST issue a warning if an author "SHOULD" requirement isn't met.

9.2. Informative References

Resources referenced informatively provide useful information relevant to this document, but do not comprise a part of its requirements.

[ARIA-PRACTICES]

WAI-ARIA
Authoring Practices. J. Scheuhammer, M. Cooper, L. Pappas,
R. Schwerdtfeger, Editors,
W3C Working Draft (work in progress), 7 March 2013. This version
of WAI-ARIA 1.0 Authoring Practices is available at http://www.w3.org/TR/2013/WD-wai-aria-practices-20130307/. Latest
version of WAI-ARIA Authoring Practices available at http://www.w3.org/TR/wai-aria-practices/.

[ARIA-PRIMER]

WAI-ARIA 1.0
Primer. L. Pappas, R. Schwerdtfeger, M. Cooper, Editors,
W3C Working Draft (work in progress), 16 September 2010. This version
of WAI-ARIA Primer is available at http://www.w3.org/TR/2010/WD-wai-aria-primer-20100916/. Latest
version of WAI-ARIA Primer available at http://www.w3.org/TR/wai-aria-primer/.

10. Appendices

10.1. Schemata

WAI-ARIA roles, states, and properties are available in a number of machine-readable formats to support validation of content using WAI-ARIA attributes. WAI-ARIA is not finalized, however, so these files are subject to change without notice.

It is not appropriate to use these document types for live content. These are made available only for download, to support local use in development, evaluation, and validation tools. Using these versions directly from the W3C server could cause automatic blockage, preventing them from loading.

10.1.1. Roles Implementation

10.1.2. WAI-ARIA Attributes Module

This module declares the WAI-ARIAattributes as a module that can be included in a modularized DTD. A sample XHTML DTD using this module follows. Note the WAI-ARIA attributes are in no namespace, and the attribute name begins with "aria-" to reduce the likelihood of collision with existing attributes.

10.1.3. XHTML plus WAI-ARIADTD

This DTD extends XHTML 1.1 and adds the WAI-ARIAstate and propertyattributes to all its elements. In order to provide broader keyboard support and conform with the Focus Navigation section above, it also adds the tabindex attribute to a wider set of elements.

This is not a formal document type and may be obsoleted by future formal XHTML DTDs that support WAI-ARIA.

Documents written using this XHTML Family markup language can be validated using the above DTD. If a document author wants to facilitate such validation, they can include the following declaration at the top of their document:

To avoid the above problem, authors can omit the above DOCTYPE statement. This causes user agents to treat the document as generic HTML with named character entity support as well as built-in ARIA support. However, it causes user agents to enter "quirks" mode which affects CSS rendering, and causes conformance checkers to fail the document due to the added ARIA attributes.

To avoid the issues of named character entity support and quirks mode, authors can instead use the following generic DOCTYPE declaration for HTML:

<!DOCTYPE html>

However, this still does not guarantee that documents will be validated by conformance checkers.

10.1.5. WAI-ARIA Attributes XML Schema Module

This module declares the WAI-ARIAattributes as an XML Schema module that can be included in a modularized schema. Note the WAI-ARIA attributes are in no namespace, and the attribute name begins with "aria-" to reduce the likelihood of collision with existing attributes.

10.1.6. HTML 4.01 plus WAI-ARIA DTD

This standalone DTD adds WAI-ARIA state and propertyattributes to all elements in HTML 4.01, as well as a role attribute. In order to provide broader keyboard support, it also adds the tabindex attribute to a wider set of elements.

The DTD is based on the HTML 4.01 Transitional DTD, and includes all entity references needed to make it a standalone file. This is not an official W3C DTD and should be considered a derivative work of HTML 4.01.

Documents written using this markup language can be validated using the above DTD. If a document author wants to facilitate such validation, they can include the following declaration at the top of their document:

To avoid the above problem, authors can omit the above DOCTYPE statement. This causes user agents to treat the document as generic HTML with named character entity support as well as built-in ARIA support. However, it causes user agents to enter "quirks" mode which affects CSS rendering, and causes conformance checkers to fail the document due to the added ARIA attributes.

To avoid the issues of named character entity support and quirks mode, authors can instead use the following generic DOCTYPE declaration for HTML:

<!DOCTYPE html>

However, this still does not guarantee that documents will be validated by conformance checkers.

The HTML Working Group is incorporating WAI-ARIA into HTML 5. Official support for WAI-ARIA in HTML will be provided in that specification. This DTD is made available only as a bridging solution for applications requiring DTD validation but not using HTML 5.

10.2. Mapping WAI-ARIA Value types to languages

Editorial note: The HTML 5 column of the table below is expected
to be moved to the HTML 5 specification and become normative
for that specification. Comments about ARIA lexicial processing in
HTML 5 should be taken to the HTML
Working Group, referencing ISSUE-129.

Editorial note: The suggested mappings for true/false values
in HTML 5 use Keyword
and enumerated attributes with allowed values of "true" and "false",
instead of using the HTML 5 boolean value type. @@ can't rely on attribute
absence because of default value in true/false/undefined case.

Languages not listed below might have appropriate value types defined in the language. If they do not, we recommend XML Schema Datatypes for general purpose XML languages. Documents using DTDs instead of schemas will not be able to validate automatically and require additional processing on WAI-ARIA attributes.

10.4.3. Enabling funders

This publication has been funded in part with Federal funds from the U.S. Department of Education, National Institute on Disability and Rehabilitation Research (NIDRR) under contract number ED05CO0039. The content of this publication does not necessarily reflect the views or policies of the U.S. Department of Education, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.